Diese Präsentation wurde erfolgreich gemeldet.
Wir verwenden Ihre LinkedIn Profilangaben und Informationen zu Ihren Aktivitäten, um Anzeigen zu personalisieren und Ihnen relevantere Inhalte anzuzeigen. Sie können Ihre Anzeigeneinstellungen jederzeit ändern.

Toyota electrical-and-engine-control-systems-manual

23.515 Aufrufe

Veröffentlicht am

Veröffentlicht in: Automobil, Technologie, Business

Toyota electrical-and-engine-control-systems-manual

  1. 1. General Electricity is a form of energy called electrical energy. It is sometimes called an "unseen" force because the energy itself cannot be seen, heard, touched, or smelled. However, the effects of electricity can be seen ... a lamp gives off light; a motor turns; a cigarette lighter gets red hot; a buzzer makes noise. The effects of electricity can also be heard, felt, and smelled. A loud crack of lightning is easily heard, while a fuse "blowing" may sound like a soft "pop" or "snap." With electricity flowing through them, some insulated wires may feel "warm" and bare wires may produce a "tingling" or, worse, quite a "shock." And, of course, the odor of burned wire insulation is easily smelled. ELECTRICAL FUNDAMENTALS Page 1 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  2. 2. Electron Theory Electron theory helps to explain electricity. The basic building block for matter, anything that has mass and occupies space, is the atom. All matter - solid, liquid, or gas - is made up of molecules, or atoms joined together. These atoms are the smallest particles into which an element or substance can be divided without losing its properties. There are only about 100 different atoms that make up everything in our world. The features that make one atom different from another also determine its electrical properties. ATOMIC STRUCTURE An atom is like a tiny solar system. The center is called the nucleus, made up of tiny particles called protons and neutrons. The nucleus is surrounded by clouds of other tiny particles called electrons. The electrons rotate about the nucleus in fixed paths called shells or rings. Hydrogen has the simplest atom with one proton in the nucleus and one electron rotating around it. Copper is more complex with 29 electrons in four different rings rotating around a nucleus that has 29 protons and 29 neutrons. Other elements have different atomic structures. ELECTRICAL FUNDAMENTALS Page 2 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  3. 3. ATOMS AND ELECTRICAL CHARGES Each atomic particle has an electrical charge. Electrons have a negative (-) charge. Protons have a positive charge. Neutrons have no charge; they are neutral. In a balanced atom, the number of electrons equals the number of protons. The balance of the opposing negative and positive charges holds the atom together. Like charges repel, unlike charges attract. The positive protons hold the electrons in orbit. Centrifugal force prevents the electrons from moving inward. And, the neutrons cancel the repelling force between protons to hold the atom's core together. POSITIVE AND NEGATIVE IONS If an atom gains electrons, it becomes a negative ion. If an atom loses electrons, it becomes a positive ion. Positive ions attract electrons from neighboring atoms to become balanced. This causes electron flow. ELECTRON FLOW The number of electrons in the outer orbit (valence shell or ring) determines the atom's ability to conduct electricity. Electrons in the inner rings are closer to the core, strongly attracted to the protons, and are called bound electrons. Electrons in the outer ring are further away from the core, less strongly attracted to the protons, and are called free electrons. Electrons can be freed by forces such as friction, heat, light, pressure, chemical action, or magnetic action. These freed electrons move away from the electromotive force, or EMF ("electron moving force"), from one atom to the next. A stream of free electrons forms an electrical current. ELECTRICAL FUNDAMENTALS Page 3 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  4. 4. CONDUCTORS, INSULATORS, SEMICONDUCTORS The electrical properties of various materials are determined by the number of electrons in the outer ring of their atoms. • CONDUCTORS - Materials with 1 to 3 electrons in the atom's outer ring make good conductors. The electrons are held loosely, there's room for more, and a low EMF will cause a flow of free electrons. • INSULATORS - Materials with 5 to 8 electrons in the atom's outer ring are insulators. The electrons are held tightly, the ring's fairly full, and a very high EMF is needed to cause any electron flow at all. Such materials include glass, rubber, and certain plastics. • SEMICONDUCTORS - Materials with exactly 4 electrons in the atom's outer ring are called semiconductors. They are neither good conductors, nor good insulators. Such materials include carbon, germanium, and silicon. CURRENT FLOW THEORIES Two theories describe current flow. The conventional theory, commonly used for automotive systems, says current flows from (+) to (-) ... excess electrons flow from an area of high potential to one of low potential (-). The electron theory, commonly used for electronics, says current flows from (-) to (+) ... excess electrons cause an area of negative potential (-) and flow toward an area lacking electrons, an area of positive potential (+), to balance the charges. While the direction of current flow makes a difference in the operation of some devices, such as diodes, the direction makes no difference to the three measurable units of electricity: voltage, current, and resistance. ELECTRICAL FUNDAMENTALS Page 4 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  5. 5. Terms Of Electricity Electricity cannot be weighed on a scale or measured into a container. But, certain electrical "actions" can be measured. These actions or "terms" are used to describe electricity; voltage, current, resistance, and power. VOLTAGE Voltage is electrical pressure, a potential force or difference in electrical charge between two points. It can push electrical current through a wire, but not through its insulation. Voltage is pressure Current is flow. Resistance opposes flow. Power is the amount of work performed. It depends on the amount of pressure and the volume of flow. Voltage is measured in volts. One volt can push a certain amount of current, two volts twice as much, and so on. A voltmeter measures the difference in electrical pressure between two points in volts. A voltmeter is used in parallel. ELECTRICAL FUNDAMENTALS Page 5 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  6. 6. CURRENT Current is electrical flow moving through a wire. Current flows in a wire pushed by voltage. Current is measured in amperes, or amps, for short. An ammeter measures current flow in amps. It is inserted into the path of current flow, or in series, in a circuit. ELECTRICAL FUNDAMENTALS Page 6 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  7. 7. RESISTANCE Resistance opposes current flow. It is like electrical "friction." This resistance slows the flow of current. Every electrical component or circuit has resistance. And, this resistance changes electrical energy into another form of energy - heat, light, motion. Resistance is measured in ohms. A special meter, called an ohmmeter, can measure the resistance of a device in ohms when no current is flowing. ELECTRICAL FUNDAMENTALS Page 7 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  8. 8. Factors Affecting Resistance Five factors determine the resistance of conductors. These factors are length of the conductor, diameter, temperature, physical condition and conductor material. The filament of a lamp, the windings of a motor or coil, and the bimetal elements in sensors are conductors. So, these factors apply to circuit wiring as well as working devices or loads. LENGTH Electrons in motion are constantly colliding as voltage pushes them through a conductor. If two wires are the same material and diameter, the longer wire will have more resistance than the shorter wire. Wire resistance is often listed in ohms per foot (e.g., spark plug cables at 5Ω per foot). Length must be considered when replacing wires. DIAMETER Large conductors allow more current flow with less voltage. If two wires are the same material and length, the thinner wire will have more resistance than the thicker wire. Wire resistance tables list ohms per foot for wires of various thicknesses (e.g., size or gauge ... 1, 2, 3 are thicker with less resistance and more current capacity; 18, 20, 22 are thinner with more resistance and less current capacity). Replacement wires and splices must be the proper size for the circuit current. TEMPERATURE In most conductors, resistance increases as the wire temperature increases. Electrons move faster, but not necessarily in the right direction. Most insulators have less resistance at higher temperatures. Semiconductor devices called thermistors have negative temperature coefficients (NTC) resistance decreases as temperature increases. Toyota's EFI coolant temperature sensor has an NTC thermistor. Other devices use PTC thermistors. PHYSICAL CONDITION Partially cut or nicked wire will act like smaller wire with high resistance in the damaged area. A kink in the wire, poor splices, and loose or corroded connections also increase resistance. Take care not to damage wires during testing or stripping insulation. MATERIAL Materials with many free electrons are good conductors with low resistance to current flow. Materials with many bound electrons are poor conductors (insulators) with high resistance to current flow. Copper, aluminum, gold, and silver have low resistance; rubber, glass, paper, ceramics, plastics, and air have high resistance. ELECTRICAL FUNDAMENTALS Page 8 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  9. 9. Voltage, Current, And Resistance In Circuits A simple relationship exists between voltage, current, and resistance in electrical circuits. Understanding this relationship is important for fast, accurate electrical problem diagnosis and repair. OHM'S LAW Ohm's Law says: The current in a circuit is directly proportional to the applied voltage and inversely proportional to the amount of resistance. This means that if the voltage goes up, the current flow will go up, and vice versa. Also, as the resistance goes up, the current goes down, and vice versa. Ohm's Law can be put to good use in electrical troubleshooting. But, calculating precise values for voltage, current, and resistance is not always practical ... nor, really needed. A more practical, less time-consuming use of Ohm's Law would be to simply apply the concepts involved: SOURCE VOLTAGE is not affected by either current or resistance. It is either too low, normal, or too high. If it is too low, current will be low. If it is normal, current will be high if resistance is low or current will be low if resistance is high. If voltage is too high, current will be high. CURRENT is affected by either voltage or resistance. If the voltage is high or the resistance is low, current will be high. If the voltage is low or the resistance is high, current will be low. RESISTANCE is not affected by either voltage or current. It is either too low, okay, or too high. If resistance is too low, current will be high at any voltage. If resistance is too high, current will be low if voltage is okay. ELECTRICAL FUNDAMENTALS Page 9 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  10. 10. ELECTRIC POWER AND WORK Voltage and current are not measurements of electric power and work. Power, in watts, is a measure of electrical energy ... power (P) equals current in amps (1) times voltage in volts (E), P = I x E. Work, in wattseconds or watt-hours, is a measure of the energy used in a period of time ... work equals power in wafts (W) times time in seconds (s) or hours (h), W = P x time. Electrical energy performs work when it is changed into thermal (heat) energy, radiant (light) energy, audio (sound) energy, mechanical (motive) energy, and chemical energy. It can be measured with a waft- hour meter. ELECTRICAL FUNDAMENTALS Page 10 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  11. 11. Actions Of Current Current flow has the following effects; motion, light or heat generation, chemical reaction, and electromagnetism. HEAT GENERATION When current flows through a lamp filament, defroster grid, or cigarette lighter, heat is generated by changing electrical energy to thermal energy. Fuses melt from the heat generated when too much current flows. CHEMICAL REACTION In a simple battery, a chemical reaction between two different metals and a mixture of acid and water causes a potential energy, or voltage. When the battery is connected to an external load, current will flow. The current will continue flowing until the two metals become similar and the mixture becomes mostly water. When current is sent into the battery by an alternator or a battery charger, however, the reaction is reversed. This is a chemical reaction caused by current flow. The current causes an electrochemical reaction that restores the metals and the acid-water mixture. ELECTROMAGNETISM Electricity and magnetism are closely related. Magnetism can be used to produce electricity. And, electricity can be used to produce magnetism. All conductors carrying current create a magnetic field. The magnetic field strength is changed by changing current ... stronger (more current), weaker (less current). With a straight conductor, the magnetic field surrounds it as a series of circular lines of force. With a looped (coil) conductor, the lines of force can be concentrated to make a very strong field. The field strength can be increased by increasing the current, the number of coil turns, or both. A strong electromagnet can be made by placing an iron core inside a coil. Electromagnetism is used in many ways. ELECTRICAL FUNDAMENTALS Page 11 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  12. 12. Types Of Electricity There are two types of electricity: static and dynamic. Dynamic electricity can be either direct current (DC) or alternating current (AC). STATIC ELECTRICITY When two non conductors - such as a silk cloth and glass rod - are rubbed together, some electrons are freed. Both materials become electrically charged. One is lacking electrons and is positively charged. The other has extra electrons and is negatively charged. These charges remain on the surface of the material and do not move unless the two materials touch or are connected by a conductor. Since there is no electron flow, this is called static electricity. DYNAMIC ELECTRICITY When electrons are freed from their atoms and flow in a material, this is called dynamic electricity. If the free electrons flow in one direction, the electricity is called direct current (DC). This is the type of current produced by the vehicle's battery. If the free electrons change direction from positive to negative and back repeatedly with time, the electricity is called alternating current (AC). This is the type of current produced by the vehicle's alternator. It is changed to DC for powering the vehicle's electrical system and for charging the battery. ELECTRICAL FUNDAMENTALS Page 12 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  13. 13. ELECTRICAL FUNDAMENTALS ASSIGNMENT NAME: 1. Describe the atomic structure of an atom and name all it’s components. 2. Explain how an ION differs from an atom. 3. Explain the difference between “bound” and “free” electrons. 4 Explain the function of the “Valence ring” 5. Define the following items: Conductors, Insulators, and Semiconductors. 6. Describe the two theories of electron flow. 7. Define in detail “voltage” and how is it measured. 8. Define in detail “current” and how is it measured. 9. Define in detail “resistance” and how is it measured. 10. Explain the relationship between current and resistance. 11. List and describe the various factors that effect resistance. 12. Explain what ohms law is and how it can be used. 13. Describe the effects of “current flow” through a conductor. 14. Describe in detail the two general categories of “electricity”. 15. Describe the two types of “dynamic electricity”.
  14. 14. Electrical Circuits A complete path, or circuit, is needed before voltage can cause a current flow through resistances to perform work. There are several types of circuits, but all require the same basic components. A power source (battery or alternator) produces voltage, or electrical potential. Conductors (wires, printed circuit boards) provide a path for current flow. Working devices, or loads (lamps, motors), change the electrical energy into another form of energy to perform work. Control devices (switches, relays) turn the current flow on and off. And, protection devices (fuses, circuit breakers) interrupt the current path if too much current flows. Too much current is called an overload, which could damage conductors and working devices. A list of five things to look for in any circuit: 1. Source of Voltage 2. Protection Device 3. Load 4. Control 5. Ground We will be identifying these items when we look at Automotive Circuits a little later in this book. ELECTRICAL CIRCUITS Page 1 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  15. 15. Types Of Circuits There are three basic types of circuits: series, parallel, and series-parallel. The type of circuit is determined by how the power source, conductors, loads, and control or protective devices are connected. SERIES CIRCUIT A series circuit is the simplest circuit. The conductors, control and protection devices, loads, and power source are connected with only one path for current. The resistance of each device can be different. The same amount of current will flow through each. The voltage across each will be different. If the path is broken, no current flows. PARALLEL CIRCUIT A parallel circuit has more than one path for current flow. The same voltage is applied across each branch. If the load resistance in each branch is the same, the current in each branch will be the same. If the load resistance in each branch is different, the current in each branch will be different. If one branch is broken, current will continue flowing to the other branches. SERIES-PARALLEL CIRCUIT A series-parallel circuit has some components in series and others in parallel. The power source and control or protection devices are usually in series; the loads are usually in parallel. The same current flows in the series portion, different currents in the parallel portion. The same voltage is applied to parallel devices, different voltages to series devices. If the series portion is broken, current stops flowing in the entire circuit. If a parallel branch is broken, current continues flowing in the series portion and the remaining branches. ELECTRICAL CIRCUITS Page 2 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  16. 16. SERIES CIRCUITS In a series circuit, current has only one path. All the circuit components are connected so that the same amount of current flows through each. The circuit must have continuity. If a wire is disconnected or broken, current stops flowing. If one load is open, none of the loads will work. Use of Ohm's Law Applying Ohm's Law to series circuits is easy. Simply add up the load resistances and divide the total resistance into the available voltage to find the current. The voltage drops across the load resistances are then found by multiplying the current by each load resistance. For calculation examples, see page 6 in the Ohms law section. Voltage drop is the difference in voltage (pressure) on one side of a load compared to the voltage on the other side of the load. The drop or loss in voltage is proportional to the amount of resistance. The higher the resistance, the higher the voltage drop. When troubleshooting, then, you can see that more resistance will reduce current and less resistance will increase current. Low voltage would also reduce current and high voltage would increase current. Reduced current will affect component operation (dim lamps, slow motors). But, increased current will also affect component operation (early failure, blown fuses). And, of course, no current at all would mean that the entire circuit would not operate. There are electrical faults that can cause such problems and knowing the relationship between voltage, current, and resistance will help to identify the cause of the problem. ELECTRICAL CIRCUITS Page 3 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  17. 17. PARALLEL CIRCUITS In a parallel circuit, current can flow through more than one path from and to the power source. The circuit loads are connected in parallel legs, or branches, across a power source. The points where the current paths split and rejoin are called junctions. The separate current paths are called branch circuits or shunt circuits. Each branch operates independent of the others. If one load opens, the others continue operating. Use of Ohm's Law Applying Ohm's Law to parallel circuits is a bit more difficult than with series circuits. The reason is that the branch resistances must be combined to find an equivalent resistance. Just remember that the total resistance in a parallel circuit is less than the smallest load resistance. This makes sense because current can flow through more than one path. Also, remember that the voltage drop across each branch will be the same because the source voltage is applied to each branch. For examples of how to calculate parallel resistance, see page 6. When troubleshooting a parallel circuit, the loss of one or more legs will reduce current because the number of paths is reduced. The addition of one or more legs will increase current because the number of paths is increased. Current can also be reduced by low source voltage or by resistance in the path before the branches. And, current can be increased by high source voltage or by one or more legs being bypassed. High resistance in one leg would affect component operation only in that leg. ELECTRICAL CIRCUITS Page 4 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  18. 18. SERIES-PARALLEL CIRCUITS In a series-parallel circuit, current flows through the series portion of the circuit and then splits to flow through the parallel branches of the circuit. Some components are wired in series, others in parallel. Most automotive circuits are series- parallel, and the same relationship between voltage, current, and resistance exists. Use of Ohm's Law Applying Ohm's Law to series-parallel circuits is a matter of simply combining the rules seen for series circuits and parallel circuits. First, calculate the equivalent resistance of the parallel loads and add it to the resistances of the loads in series. The total resistance is then divided into the source voltage to find current. Voltage drop across series loads is current times resistance. Current in branches is voltage divided by resistance. For calculation examples, see page 6. When troubleshooting a series-parallel circuit, problems in the series portion can shut down the entire circuit while a problem in one leg of the parallel portion may or may not affect the entire circuit, depending on the problem. Very high resistance in one leg would reduce total circuit current, but increase current in other legs. Very low resistance in one leg would increase total circuit current and possibly have the effect of bypassing other legs. ELECTRICAL CIRCUITS Page 5 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  19. 19. Ohm's Law Fast, accurate electrical troubleshooting is easy when you know how voltage, current, and resistance are related. Ohm's Law explains the relationship: • Current (amps) equals voltage (volts) divided by resistance (ohms) ... I = E ÷ R. • Voltage (volts) equals current (amps) times resistance (ohms) ... E = I X R. • Resistance (ohms) equals voltage (volts) divided by current (amps) ... R ÷ E = 1. USING OHM'S LAW The effects of different voltages and different resistances on current flow can be seen in the sample circuits. Current found by dividing voltage by resistance. This can be very helpful when diagnosing electrical problems: • When the resistance stays the same ... current goes up as voltage goes up, and current goes down as voltage goes down. A discharged battery has low voltage which reduces current. Some devices may fail to operate (slow motor speed). An unregulated alternator may produce too much voltage which increases current. Some devices may fail early (burned-out lamps). • When the voltage stays the same ... current goes up as resistance goes down, and current goes down as resistance goes up. Bypassed devices reduce resistance, causing high current. Loose connections increase resistance, causing low current. ELECTRICAL CIRCUITS Page 6 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  20. 20. SAMPLE CALCULATIONS Here are some basic formulas you will find helpful in solving more complex electrical problems. They provide the knowledge required for confidence and thorough understanding of basic electricity. The following abbreviations are used in the formulas: E = VOLTS I = AMPS R = OHMS P = WATTS • Ohm's Law Scientifically stated, it says: "The intensity Of the current in amperes in any electrical circuit is equal to the difference in potential in volts across the circuit divided by the resistance in ohms of the circuit." Simply put it means that current is equal to volts divided by ohms, or expressed as a formula, the law becomes: I = E / R or it can be written: E = I X R This is important because if you know any two of the quantities, the third may be found by applying the equation. Ohm's law includes these two ideas: 1. In a circuit, if resistance is constant, current varies directly with voltage. Now what this means is that if you take a component with a fixed resistance, say a light bulb, and double the voltage you double the current flowing through it. Anyone who has hooked a six- volt bulb to a twelve-volt circuit has experienced this. But it wasn't "too many volts" that burned out the bulb, it was too much current. More about that later. 2. In a circuit, if voltage is constant, current varies inversely with resistance. This second idea states that when resistance goes up, current goes down. That's why corroded connectors cause very dim lights - not enough current. • Watts A watt is an electrical measurement of power or work. It directly relates to horsepower. In fact, in the Sl metric standards that most of the world uses, engine power is given in watts or kilowatts. Electrical power is easily calculated by the formula: P = E X I For instance, a halogen high-beam headlight is rated or 5 amps of current. Figuring 12 volts in the system, we could write: P = E X I P = 12 X 5 P = 60 watts ELECTRICAL CIRCUITS Page 7 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  21. 21. RESISTANCE The effect of individual resistors on the total resistance of a circuit depends on whether the circuit is series or parallel. Series Circuits In a series circuit, the total resistance is equal to the sum of the individual resistors: SERIES: total R = R1 + R2 + R3 + That is the basis of the concept of voltage drop. For example, if you had a circuit with three loads in series (a bulb, resistor, and corroded ground) you would add the three together to get total resistance. And, of course, the voltage would drop across each load according to its value. Parallel Circuits Parallel circuits are a different story. In a parallel circuit, there are three ways to find total resistance. Method A works in all cases. Method B works only if there are two branches, equal or not. Method C works only if the branches are of equal resistance. A. The total resistance is equal to one over the sum of the reciprocals of the individual resistors. That sounds confusing, but looking at the formula will make it clearer: PARALLEL: n example will make it even clearer. Suppose there is a circuit with three resistors in parallel: 4 ohms, 2 ohms, and 1 ohm. The formula would look like this: That becomes: Which becomes: So there is a little more than one-half ohm resistance in the circuit. You can see that the more resistors in parallel, the less the resistance. In fact, the total resistance is always less than the smallest resistor. This is why a fuse will blow if you add too many circuits to the fuse. There are so many paths for the current to follow that the total resistance of the circuit is very low. That means the current is very high - so high that the fuse can no longer handle the load. B. For two resistors: For a 3 ohm and a 5 ohm resistor that would be: C. For several identical resistors, divide the value of one resistor by the number of resistors, or: Where R1 is the value of one resistor and n is the number of resistors. So if you had three 4 ohm resistors in parallel it would be: ELECTRICAL CIRCUITS Page 8 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  22. 22. ELECTRICAL CIRCUITS Page 9 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  23. 23. ELECTRICAL CIRCUITS ASSIGNMENT NAME: 1. Draw and label the parts of a Series Circuit and a Parallel Circuit. 2. Explain the characteristics of “Voltage” and how it differs between a Series Circuit and a Parallel Circuit. 3. Explain the characteristics of “Current” and how it differs between a Series Circuit and a Parallel Circuit. 4. Explain the characteristics of “Resistance” and how it differs between a Series Circuit and a Parallel Circuit.
  24. 24. Power Sources On The Car Two power sources are used on Toyota vehicles. When the engine is not running or is being started, the battery provides power. When the engine is running, the alternator provides power for the vehicle's loads and for recharging the battery. THE BATTERY The battery is the primary "source" of electrical energy on Toyota vehicles when the engine is not running or is being started. It uses an electrochemical reaction to change chemical energy into electrical energy for starting, ignition, charging, lighting, and accessories. All Toyota vehicles use a 12-volt battery. Batteries have polarity markings ... the larger (thicker) terminal is marked "plus" or "POS" (+), the other terminal is marked “minus" or "NEG" (-). Correct polarity is important; components can be damaged if the battery is connected backwards. THE ALTERNATOR The alternator is the heart of the vehicle's electrical system when the engine is running. It uses electromagnetism to change some of the engine's mechanical energy into electrical energy for powering the vehicle's loads and for charging the battery. All Toyota alternators are rated by amps of current output ... from 40 to 80 amps. ELECTRICAL COMPONENTS Page 1 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  25. 25. Loads Working devices - or loads - consume electricity. They change electrical energy into another form of energy to do work. This energy may be thermal (heat), radiant (light), mechanical (motive), audio (sound), chemical, or magnetic. The electrical energy is changed by the resistance of the working device. Resistance is put to work in many ways on Toyota vehicles. PERFORM WORK Some components use resistance to reduce current flow and change electrical energy (voltage) into heat, light, or motion. Resistance produces heat in electric window defrosters and cigarette lighters. Resistance produces light in lamp filaments. And, resistance produces motion in motors and solenoid coils. All circuit loads use resistance to perform work. CONTROL CURRENT Other components and systems use resistance for current control. Ignition primary resistors, also called ballast resistors, maintain and protect the electronic control unit (ECU) from excessive current. The headlamp rheostat adds or subtracts resistance to dim or brighten interior lamps. A carbon pile resistance in the Sun VAT-40 tester "loads" the battery for cranking-voltage and charging system tests. A sliding contact resistance is used on some A/C and heating controls to adjust interior temperature by increasing or decreasing air volume and fan speed. A wire-wound resistor is used on some fuel pumps to reduce pump speed. REDUCE ARCING AND "RFI" Some ignition components use resistance to reduce arcing and radio frequency interference (RFI). Condensers use the high resistance of a dielectric (insulating) material to separate conductive plates that soak up electrostatic charges and current surges that cause RFI and point arcing. Spark plug cables, also called carbon resistance wires, reduce current flow but transmit high voltage to the spark plugs. This causes an extremely hot spark without RFI or rapid burning of the plug electrodes. Spark plugs, themselves, have a carbon core to achieve the same results. SENSE OPERATING CONDITIONS Other components use resistance in sensing and monitoring operating conditions. The resistance added to or subtracted from a sensing circuit changes the current flow which is used for input to a control device, gauge, or actuator. The coolant temperature sensor uses a device that changes resistance with temperature. The fuel-level sensor uses a type of potentiometer, or sliding-contact resistance. The automatic headlamp control uses a photoresistor. The manifold vacuum sensor uses a crystal which changes resistance with pressure. And, with the use of electronic control systems growing rapidly, many more sensors and actuators are using the variation of resistance to operate. ELECTRICAL COMPONENTS Page 2 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  26. 26. Types Of Resistors Three basic types of resistors are use a m automotive electrical systems ... fixed value, stepped or tapped, and variable. Different symbols are used for the different types of resistors. FIXED-VALUE RESISTORS Two types of fixed-value resistors are used: wire- wound and carbon. Wire-wound resistors are made with coils of resistance wire. Sometimes called power resistors, they are very accurate and heat stable. The resistance value is marked. Carbon resistors are common in Toyota electronic systems. Carbon is mixed with binder; the more carbon, the lower the resistance. Some have the resistance value stamped on, others are rated by wafts of power; most have color-code bands to show the resistance value. Four bands are used ... the first two bands give the resistance digits, the next band is the number of zeros, and the last band gives the "tolerance." A resistor with four bands - red, green, black, and brown from left to right - would be sized as follows: • The first two bands set the digits ... red (2), green (5). • The next band is the number of zeros. Black is "0" zeros. So the resistor has a base value of 25Ω. • And, the last band is the tolerance ... brown (1 %). So, the resistance value is "25 ohms plus or minus .25 ohms" (24.75Ω to 25.25Ω ). ELECTRICAL COMPONENTS Page 3 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  27. 27. STEPPED OR TAPPED RESISTORS Stepped or tapped resistors have two or more fixed resistance values. The different resistances (carbon or wire) are connected to different terminals in a switch. As the switch is moved, different resistance values are placed in the circuit. A typical Toyota application is in the heater motor's blower-fan switch. VARIABLE RESISTORS Three types of variable resistors are used: rheostats, potentiometers, and thermistors. • RHEOSTAT - Toyota uses a rheostat on the headlamp switch to dim or brighten dash panel lighting. Rheostats have two connections ... one to the fixed end of a resistor, one to a sliding contact on the resistor. Turning the control moves the sliding contact away from or toward the fixed end, increasing or decreasing the resistance. • POTENTIOMETER - Toyota uses a potentiometer in the EFI airflow meter. Potentiometers have three connections ... one at each end of a resistor and one on a sliding contact. Turning the control places more or less resistance in the circuit. • THERMISTOR - Toyota uses NTC (negative temperature coefficient) thermistors in temperature sensors and PTC (positive temperature coefficient) thermistors in the electric assist choke. Both types of thermistors change resistance with increasing temperature (NTC, resistance goes down as temperature goes up; PTC, resistance goes up as temperature go up.) ELECTRICAL COMPONENTS Page 4 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  28. 28. Controls Control devices used in electrical circuits on Toyota vehicles include a variety of switches, relays, and solenoids. Electronic control devices include capacitors, diodes, and transistors. Controls are needed to start, stop, or redirect current flow. Most switches require physical movement for operation, relays and solenoids are operated with electromagnetism, electronic controls are operated electrically. SWITCHES Switches are the most common circuit control device. They usually have two or more sets of contacts. Opening the contacts is called "opening" or "breaking the circuit," while closing the contacts is called "closing" or "making" the circuit. "Poles" refer to the number of input circuit terminals. "Throws" refer to the number of output circuits. Such switches are referred to as SPST (single- pole, single-throw), SPDT (single-pole, double- throw), and MPMT (multiple-pole, multiple-throw). The various types of switches include: • Hinged pawl - a simple SPST switch to make or break a circuit. • Momentary contact - another SPST switch, normally open or closed, which makes or breaks the circuit when pressed ... typically used for the horn switch. • SPDT - one wire in, two wires out ... commonly used in high-beam / low-beam headlamp circuits. • MPMT - movable contacts are linked to sets of output terminals ... may be used for the transmission neutral start switch. • Mercury switch - liquid mercury flows between contacts to make circuit ... commonly used to turn engine compartment and trunk lamps on and off. • Temperature-sensitive switch - a bimetal element bends when heated to make contact completing a circuit or to break contact opening a circuit. The same principle is also used in time- delay switches and flashers. ELECTRICAL COMPONENTS Page 5 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  29. 29. RELAYS A relay is simply a remote-control switch, which uses a small amount of current to control a large amount of current. A typical relay has a control circuit and a power circuit. The control circuit is fed current by the power source, and the current flows through a switch and an electromagnetic coil to ground. The power circuit is also fed current from the power source, and the current flows to an armature which can be attracted by the magnetic force on the coil. In operation, when the control circuit switch is open, no current flows to the relay. The coil is not energized, the contacts are open, and no power goes to the load. When the control circuit switch is closed, however, current flows to the relay and energizes the coil. The resulting magnetic field pulls the armature down, closing the contacts and allowing power to the load. Many relays are used on Toyotas for controlling high current in one circuit with low current in another circuit. The relay control circuit can be switched from the power supply side or, more common in Toyotas, from the ground side. SOLENOIDS Solenoids are electromagnetic switches with a movable core that converts current flow into mechanical movement. In a "pulling" type solenoid, the magnetic field pulls a core into a coil. These solenoids are called magnetic switches on Toyota starters. A pull-in coil "pulls" the core into the coil, and a hold-in coil "holds" the core in place. In a "push-pull" type solenoid, a permanent magnet is used for the core. By changing the direction of current flow, the core is "pulled in" or "pushed out." A typical use is on electric door locks. ELECTRICAL COMPONENTS Page 6 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  30. 30. CAPACITORS Capacitors use an electrostatic field to "soak up" or store an electrical charge. In a circuit, a capacitor will build up a charge on its negative plate. Current flows until the capacitor charge is the same as that of the power source. It will hold this charge until it is discharged through another circuit (such as ground). Always handle capacitors with care; once charged, they can be quite shocking long after the power is removed. • TYPES A capacitor has two conducting plates separated by an insulating material or dielectric. Three types are used: ceramic for electronic circuits, paper and foil for noise suppression in charging and ignition systems, and electrolytic for turn-signal flashers. Different symbols are used for ordinary and electrolytic capacitors. • RATINGS Automotive capacitors are rated in microfarads, and the rating is usually stamped on the case. Always choose a capacitor rated for the maximum expected voltage. • DIAGNOSIS / TESTING Capacitors can be tested for short circuits using an ohmmeter. Connect one test lead to the capacitor mounting clip and the other test lead to the capacitor pigtail connector. The meter needle will first show some continuity as the meter's battery charges the capacitor, then will swing to infinite resistance (∞). If only continuity is seen, the capacitor is most likely shorted. ELECTRICAL COMPONENTS Page 7 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  31. 31. Electronics "Electronic" devices and systems provide today's vehicles with added comfort, convenience, safety, and performance. These devices and systems, like their "electrical" counterparts, control electricity to do work. The current flows through a semiconductor - rather than through wires. The movement usually produces an electrical signal - rather than heat, light, or motion. And, this signal may be transmitted, amplified, or used in special circuits to perform logical decision-making functions. Since there are seldom any moving (electromechanical) parts, these devices and systems are often called solid-state electronics. SEMICONDUCTORS Semiconductors can act like conductors or insulators. They have a resistance higher than that of conductors like copper or iron, but lower than that of insulators like glass or rubber. They have special electrical properties: • Conductivity can be increased by mixing in certain substances; • Resistance can be changed by light, temperature, or mechanical pressure; and, • Light can be produced by passing current through them. DIODES Diodes are semiconductor devices which act as one way electrical check valves. Diodes will allow current flow in one direction (anode to cathode), but block it in the reverse direction (cathode to anode). • TYPES / USES There are several types of diodes. Rectifying diodes change low-current AC to DC in the charging system. Power rectifiers can handle larger currents in electronic power supplies. Zener diodes can function as voltage sensitive switches. They turn "on" to allow current flow once a certain voltage is reached. They are often used in voltage regulation applications. Light- emitting diodes (LEDs) are used for indicator lights and digital displays. And, photodiodes detect light for sensors. • SYMBOLS Symbols for various diodes are shown. The arrow points in the "forward" direction of current flow (anode to cathode). Zener diodes have a "Z" shaped bar on the cathode side. LEDs and photodiodes are enclosed in a circle with incoming or outgoing light indicated. ELECTRICAL COMPONENTS Page 8 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  32. 32. Transistors Transistors are semiconductor devices for controlling current flow. A "transistor" (transformer + resistor) transfers signals across the resistance of two semiconductor materials. • TYPES / USES There are many types of transistors. Ordinary or bipolar transistors are most common for switching and amplifying. Power transistors are a variation for larger currents; exposed metal carries away heat. Phototransistors are another variation, used as light-sensitive switches in speedometer and headlamp systems. Field-effect transistors (FETs) are quite different. They are used as switches, amplifiers, and voltage controlled resistors. • SYMBOLS Bipolar transistors are shown with a line and arrow for the emitter, a heavy T-shaped line for the base, and a line without an arrow for the collector. The emitter arrow points to the circuit's negative side. Phototransistors have incoming light arrows added. And, FETs have an arrow showing negative (N) or positive (P) voltage. • OPERATION In bipolar transistors, a small base current (I b) between the emitter-base "turns on" the transistor and causes a larger current (I c) to flow between the emitter-collector. In phototransistors, light striking the base "turns on" the transistor. This switches on a second transistor which amplifies the signal. ELECTRONIC CIRCUITS AND SYSTEMS Individual semiconductor devices are called discrete devices, a number of them may be used in a circuit. Such devices are common in charging, ignition, and headlamp circuits that handle large amounts of power. The more sophisticated electronic control systems now being used on the vehicle, however, make use of integrated circuits and microprocessors or onboard computers. • INTEGRATED CIRCUITS An integrated circuit (IC) has hundreds, even thousands, of discrete devices on a single silicon chip. These include diodes, transistors, resistors, and capacitors. The IC is usually packaged in ceramic or plastic and each tiny device inside is connected to one or more leads that plug into a larger on-vehicle circuit. One type can process analog signals - those that change continuously with time. Another type can process digital signals - those that change intermittently "on" or "off" with time. • MICROPROCESSORS Microprocessors, or on-board computers, are used on various electronic control systems. Such systems have three basic parts: 1) sensors tell what is happening; 2) the microprocessor computes the data and decides what to do; and 3) the actuators or controls respond to change or display the condition. The ECS and ABS are examples of such systems. ELECTRICAL COMPONENTS Page 9 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  33. 33. Protective Devices Electrical circuits are protected from too much current by fuses, fusible links, and circuit breakers. Such devices will interrupt a circuit to prevent high current from melting conductors and damaging loads. Each of these circuit protection devices is sensitive to current, not voltage, and is rated by current-carrying capacity. They are usually located at, or near, the power source for the circuit being protected. As such, they are usually a good starting point during electrical problem troubleshooting. Remember, though, these devices "blow" or open a circuit because of a problem. Always locate and correct the problem before replacing a fuse or fusible link or resetting a circuit breaker. FUSES Fuses are the most common circuit protection device. Fuses have a fusible element, or low- melting-point metal strip, in a glass tube or plug-in plastic cartridge. These fuses are located in a fuse block under the dash or behind a kick panel. Most circuits - other than the headlamp, starter, and ignition systems - receive power through the fuse block. Battery voltage is supplied to a buss bar in the block. One end of each fuse is connected to this bar, the other end to the circuit it protects. Fuse ratings range from 0.5 to 35 amps, but 7.5 - amp to 20-amp fuses are most common. ELECTRICAL COMPONENTS Page 10 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  34. 34. FUSIBLE LINKS Some circuits use fusible links, or fuse links, for overload protection. Toyotas can have as many as six fusible links protecting circuits for charging, starting, ignition, and certain accessories. Check the "Power Source" page in the Electrical Wiring Diagram manual for the specific vehicle. A fusible link is a short length of smaller gauge wire installed in a circuit with larger conductors. High current will melt the link before it melts the circuit wiring. Such fuse links have special insulation that blisters or bubbles when the link melts. A melted link must be replaced with one of the same size after the cause of the overload has been identified and the problem corrected. CIRCUIT BREAKERS Circuit breakers are used for protecting circuits temporary overloads may occur and where power must be quickly restored. A bimetal strip is used, similar to that in a temperature-sensitive switch. When heated, the two metals expand differently and cause the strip to bend. The "breaker" is normally closed and it opens when the bimetal element bends. Some circuit breakers are self- resetting, others must be manually reset. Circuit breakers are used on Toyota vehicles to protect circuits for the defogger, heater, air conditioner, power windows, power door locks, and sun roof. ELECTRICAL COMPONENTS Page 11 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  35. 35. ELECTRICAL COMPONENTS ASSIGNMENT NAME: 1. Describe two power sources used in a vehicle. 2. Explain the term “load” and how it is used in a circuit. 3. Describe the two types of resistors and how each is used. 4. Explain the color code of a resistor that is: “Brown, Orange, Red, Silver. 5. Describe a “stepped resistor “ and how it differs from a “fixed resister”. 6. List and describe three types of “variable resistors”. 7. Explain how a “NTC” thermistor differs from a “PTC” thermistor. 8. List six types of switches used in automobiles. 9. Describe the two circuits used in a relay. 10 Explain how a “relay” differs from a “solenoid”. 11. Explain how current flows into a “capacitor”. 12. Explain the term “semiconductor”. 13. Draw, label, and describe the basic function of a “diode”. 14. Draw, label, and describe the basic function of a “bi-polar transistor”. 15. Explain the term “Integrated Circuit”. 16. List three types of “circuit protective devices”. 17. Describe the basic construction of a “fuse” or “fuse element”. 18. Explain how a “fuse element” differs from a “fusible link”. 19. Describe the basic construction of a “circuit breaker”.
  36. 36. ANALOG VS. DIGITAL METERS Ultimately, your diagnosis of vehicle electrical system problems will come down to using a voltmeter, ammeter, or ohmmeter to pinpoint the exact location of the problem. There are two types of each meter—analog and digital. Analog meters use a needle and calibrated scale to indicate values. Digital meters display those values on a digital display. This chapter will help you understand how these meters work as well as the advantages and disadvantages of each. Before using a meter, read the manufacturer's operating instructions. Reading analog meters usually requires simple mental calculations. For example, a meter might have three voltage ranges: 4.0 V, 20 V and 40 V, but only two scales: 4.0 V and 20 V. In order to use the 40 V range, you need to multiply the needle reading on the 4.0 V scale by 10 (or for that matter, the 20 V scale by 2). Digital meters are usually simpler to read and many will adjust to the proper range required for the circuit or device they are connected to. These meters are known as auto-ranging meters. Other digital meters require the operator to select the proper range. In any case it is important to learn the symbols used in a digital readout so you can interpret the reading. The electrical units of measure symbols are: M for mega or million K for kilo or thousand m for milli or one-thousandth u for micro or one-millionth The three types of meters—voltmeters, ammeters and ohmmeters—connect to the circuits or devices in different ways. This is necessary to get accurate measurements and to prevent damage to the meters. VOLTMETERS— ANALOG AND DIGITAL Voltmeters measure voltage or voltage drop in a circuit. Voltage drop can be used to locate excessive resistance in the circuit which could cause poor performance or improper operation. Lack of voltage at a given point may indicate an open circuit or ground. On the other hand, low voltage or high voltage drop, may indicate a high resistance problem like a poor connection. Voltmeters must be connected in parallel with the device or circuit so that the meter can tap off a small amount of current. That is, the positive or red lead is connected to the circuit closest to the positive side of the battery. The negative or black lead is connected to ground or the negative side of the circuit. If a voltmeter is connected in series, its high resistance would reduce circuit current and cause a false reading. ANALOG AND DIGITAL METERS Page 1 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  37. 37. Because voltmeters are always hooked to a circuit in parallel, they become part of the circuit and reduce the total resistance of the circuit. If a voltmeter has a resistance that is too low in comparison to the circuit, it will give a false measurement. The false reading is due to the meter changing the circuit by lowering the resistance, which increases the current flow in the circuit. The effect a voltmeter has on the circuit to which it is attached is sometimes referred to as "loading effect" of the meter. The loading effect a voltmeter has on a circuit is determined by the total resistance of the circuit in relation to the impedance of the voltmeter. Every voltmeter has an impedance, which is the meter's internal resistance. The impedance of a conventional analog voltmeter is expressed in "ohms per volt." The amount of resistance an analog voltmeter represents to the circuit changes in relation to the scale on which it is placed. Digital voltmeters, on the other hand, have a fixed impedance which does not change from scale to scale and is usually 10 M ohms or more. Impedance is the biggest difference between analog and digital voltmeters. Since most digital voltmeters have 50 times more impedance than analog voltmeters, digital meters are more accurate when measuring voltage in high resistance circuits. For example, if you are using a low impedance (20,000 ohms per volt) analog meter on the 20 volt scale (the voltmeter represents 400,000 ohms resistance to the circuit) to measure voltage drop across a 1,000,000 ohm component in a circuit, two and a half times as much current is flowing through the meter than through the component. You are no longer measuring just that component, but the component plus your meter, giving you a false reading of the actual voltage drop across the component. This situation might lead you to believe the voltage at the component is low or that there is high resistance somewhere in the circuit or that the component is defective when it is just the meter you are using. If you use a digital meter with 10 million ohms of impedance to test the same component, only 1/10 of the current will flow through the meter, which means it has very little effect on the circuit being measured. ANALOG AND DIGITAL METERS Page 2 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  38. 38. AMMETERS— ANALOG AND DIGITAL Ammeters measure amperage, or current flow, in a circuit, and provide information on current draw as well as circuit continuity. High current flow indicates a short circuit, unintentional ground or a defective component. Some type of defect has lowered the circuit resistance. Low current flow may indicate high resistance or a poor connection in the circuit or a discharged battery. No current indicates an open circuit or loss of power. Ammeters must always be connected in series with the circuit, never in parallel. That is, all the circuit current must flow through the meter. It is connected by attaching the positive lead to the positive or battery side of the circuit, and the negative lead to negative or ground side of the circuit, as shown. CAUTION: These meters have extremely low internal resistance. If connected in parallel, the current running through the parallel branch created by the meter might be high enough to damage the meter along with the circuit the meter is connected to. Also, since all the current will flow through the ammeter when it is connected be sure that the circuit current will not exceed the maximum rating of the meter. There is not a great difference between analog and digital ammeters. Digital meters are often capable of measuring smaller currents, all the way down to microamps. They are easier to use because they give a specific value, eliminating the need to interpret the analog meter's needle on its scale. Generally speaking, most digital ammeters are combined with a voltmeter. OHMMETERS— ANALOG AND DIGITAL An ohmmeter is powered by an internal battery that applies a small voltage to a circuit or component and measures how much current flows through the circuit or component. It then displays the result as resistance. Ohmmeters are used for checking continuity and for measuring the resistance of components. Zero resistance indicates a short while infinite resistance indicates an open in a circuit or device. A reading higher than the specification indicates a faulty component or a high resistance problem such as burnt contacts, corroded terminals or loose connections. ANALOG AND DIGITAL METERS Page 3 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  39. 39. Ohmmeters, because they are self- powered, must never be connected to a powered circuit as this may blow a fuse in the meter and damage its battery. Unless the circuit being measured contains a diode, polarity (attaching the leads in a particular order) is inconsequential. An analog ohmmeter should be calibrated regularly by connecting the two leads together and zeroing the meter with the adjust knob. This compensates for changes in the state of charge of the internal battery. CAUTION: Analog ohmmeters may apply a higher voltage to a circuit than a digital ohmmeter, causing damage to solid state components. Use analog ohmmeters with care. Digital meters, on the other hand, apply less voltage to a circuit, so damage is less likely. Analog meters can also bias, or turn on, semi-conductors and change the circuit by allowing current to flow to other portions of the circuit. Most digital meters have a low voltage setting which will not bias semi- conductors and a higher voltage setting for testing semiconductors. The information displayed on a digital meter in the diode test function differs from one meter brand to another. Some digital meters will display a value which represents the perceived resistance of the diode in forward bias. Other meters will display the forward bias voltage drop of the diode. Digital ohmmeters do have one limitation. Due to the small amount of current they pass through the device being tested, they cannot check some semiconductors in circuits, such as a clamping diode on a relay coil. Many analog ohmmeters will, when switched to the ohm function, reverse the polarity of the test leads. In other words, the red lead may become negative and the black lead may become positive. The meter will function properly as long as you are aware of this and reverse the leads. This is especially important when working with diodes or transistors which are polarity sensitive and only allow current to flow from the positive to the negative end. To check for polarity reversal, set the ohmmeter in ohm function and connect its leads to the leads of a voltmeter (red to red, black to black). If the voltmeter shows a negative value, that particular ohmmeter reverses polarity in ohm function. Most digital meters do not reverse polarity. You should note that ohmmeters do little good in low resistance, high current- carrying circuits such as starters. They cannot find points of high resistance because they only use a small amount of current from their internal batteries. In a large conductor (such as a battery cable), this current meets little resistance. A voltage drop test during circuit operation is much more effective at locating points of high resistance in this type of circuit. Taken with permission from the Toyota Advanced Electrical Course#672, ANALOG AND DIGITAL METERS Page 4 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  40. 40. ANALOG AND DIGITALMETERS ASSIGNMENT NAME: 1. Explain how reading an Analog meter differs from a Digital meter. 2. Explain the following electrical units of measure symbols ( M, K, m, u ). 3. List three types of meters. 4. Describe how voltmeters are connected to a circuit. 5. Explain how “meter loading” affects the circuit. 6. Describe “meter impedance” and how it effects a circuit? 7. List the fixed impedance value of a digital voltmeter. 8. Explain how the impedance of a digital meter differs from an analog meter. 9. Describe how ammeters are connected to a circuit. 10. Explain how analog ohmmeters differ from digital ohmmeters in setup. 11. Explain what precautions one should take while connecting an ohmmeter to a circuit.
  41. 41. CONDUCTORS Conductors are needed to complete the path for electrical current to flow from the power source to the working devices and back to the power source. POWER OR INSULATED CONDUCTORS Conductors for the power or insulated current path may be solid wire, stranded wire, or printed circuit boards. Solid, thin wire can be used when current is low. Stranded, thick wire is used when current is high. Printed circuitry - copper conductors printed on an insulating material with connectors in place - is used where space is limited, such as behind instrument panels. Special wiring is needed for battery cables and for ignition cables. Battery cables are usually very thick, stranded wires with thick insulation. Ignition cables usually have a conductive carbon core to reduce radio interference. GROUND PATHS Wiring is only half the circuit in Toyota electrical systems. This is called the "power" or insulated side of the circuit. The other half of the path for current flow is the vehicle's engine, frame, and body. This is called the ground side of the circuit. These systems are called single-wire or ground-return systems. A thick, insulated cable connects the battery's positive ( + ) terminal to the vehicle loads. As insulated cable connects the battery's negative ( - ) cable to the engine or frame. An additional grounding cable may be connected between the engine and body or frame. Resistance in the insulated side of each circuit will vary depending on the length of wiring and the number and types of loads. Resistance on the ground side of all circuits must be virtually zero. This is especially important: Ground connections must be secure to complete the circuit. Loose or corroded ground connections will add too much resistance for proper circuit operation. SYSTEM POLARITY System polarity refers to the connections of the positive and negative terminals of the battery to the insulated and ground sides of the electrical system. On Toyota vehicles, the positive (+) battery terminal is connected to the insulated side of the system. This is called a negative ground system having positive polarity. Knowing the polarity is extremely important for proper service. Reversed polarity may damage alternator diodes, cause improper operation of the ignition coil and spark plugs, and may damage other devices such as electronic control units, test meters, and instrument panel gauges. WIRE, TERMINAL AND CONNECTOR REPAIR Page 1 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  42. 42. HARNESSES Harnesses are bundles of wires that are grouped together in plastic tubing, wrapped with tape, or molded into a flat strip. The colored insulation of various wires allows circuit tracing. While the harnesses organize and protect wires going to common circuits, don't over look the possibility of a problem inside. WIRE INSULATION Conductors must be insulated with a covering or "jacket." This insulation prevents physical damage, and, more important, keeps the current flow in the wire. Various types of insulation are used depending on the type of conductor. Rubber, plastic, paper, ceramics, and glass are good insulators. CONNECTORS Various types of connectors, terminals, and junction blocks are used on Toyota vehicles. The wiring diagrams identify each type used in a circuit. Connectors make excellent test points because the circuit can be "opened" without need for wire repairs after testing. However, never assume a connection is good simply because the terminals seem connected. Many electrical problems can be traced to loose, corroded, or improper connections. These problems include a missing or bent connector pin. WIRE, TERMINAL AND CONNECTOR REPAIR Page 2 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  43. 43. CONNECTOR REPAIR The repair parts now in supply are limited to those connectors having common shapes and terminal cavity numbers. Therefore, when there is no available replacement connector of the same shape or terminal cavity number, please use one of the alternative methods described below. Make sure that the terminals are placed in the original order in the connector cavities, if possible, to aid in future diagnosis. 1 . When a connector with a different number of terminals than the original part is used, select a connector having more terminal cavities than required, and replace both the male and female connector parts. Example: You need a connector with six terminals, but the only replacement available is a connector with eight terminal cavities. Replace both the male and female connector parts with the eight terminal part, transfering the terminals from the old connectors to the new connector. 2. When several different type terminals are used in one connector, select an appropriate male and female connector part for each terminal type used, and replace both male and female connector parts. Example: You need to replace a connector that has two different types of terminals in one connector. Replace the original connector with two new connectors, one connector for one type of terminal, another connector for the other type of terminal. 3. When a different shape of connector is used, first select from available parts a connector with the appropriate number of terminal cavities, and one that uses terminals of the same size as, or larger than, the terminal size in the vehicle. The wire lead on the replacement terminal must also be the same size as, or larger than, the nominal size of the wire in the vehicle. ("Nominal" size may be found by looking at the illustrations in the back of this book or by direct measurement across the diameter of the insulation). Replace all existing terminals with the new terminals, then insert the terminals into the new connector. Example: You need to replace a connector that is round and has six terminal cavities. The only round replacement connector has three terminal cavities. You would select a replacement connector that has six or more terminal cavities and is not round, then select terminals that will fit the new connector. Replace the existing terminals, then insert them into the new connector and join the connector together. WIRE, TERMINAL AND CONNECTOR REPAIR Page 3 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  44. 44. CONDUCTOR REPAIR Conductor repairs are sometimes needed because of wire damage caused by electrical faults or by physical abuse. Wires may be damaged electrically by short circuits between wires or from wires to ground. Fusible links may melt from current overloads. Wires may be damaged physically by scraped or cut insulation, chemical or heat exposure, or breaks caused during testing or component repairs. WIRE SIZE Choosing the proper size of wire when making circuit repairs is critical. While choosing wires too thick for the circuit will only make splicing a bit more difficult, choosing wires too thin may limit current flow to unacceptable levels or even result in melted wires. Two size factors must be considered: wire gauge number and wire length. • WIRE GAUGE NUMBER Wire gauge numbers are determined by the conductor's cross-section area. In the American Wire Gauge system, "gauge" numbers are assigned to wires of different thicknesses. While the gauge numbers are not directly comparable to wire diameters and cross- section areas, higher numbers (16, 18, 20) are assigned to increasingly thinner wires and lower numbers (1, 0, 2/0) are assigned to increasingly thicker wires. The chart shows AWG gauge numbers for various thicknesses. Wire cross-section area in the AWG system is measured in circular mils. A mil is a thousandth of an inch (0.001). A circular mil is the area of a circle 1 mil (0.001) in diameter. In the metric system used worldwide, wire sizes are based on the cross-section area in square millimeters (mm 2 ). These are not the same as AWG sizes in circular mils. The chart shows AWG size equivalents for various metric sizes. • WIRE LENGTH Wire length must be considered when repairing circuits because resistance increases with longer lengths. For instance, a 16-gauge wire can carry an 18-amp load for 10 feet without excessive voltage drop. But, if the section of wiring being replaced is only 3-feet long, an 18-gauge wire can be used. Never use a heavier wire than necessary, but - more important - never use a wire that will be too small for the load. WIRE, TERMINAL AND CONNECTOR REPAIR Page 4 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  45. 45. WIRE REPAIRS • Cut insulation should be wrapped with tape or covered with heat-shrink tubing. In both cases, overlap the repair about 1/2-inch on either side. • If damaged wire needs replacement, make sure the same or larger size is used. Also, attempt to use the same color. Wire strippers will remove insulation without breaking or nicking the wire strands. • When splicing wires, make sure the battery is disconnected. Clean the wire ends. Crimp and solder them using rosin-core, not acid-core, solder. • SOLDERING Soldering joins two pieces of metal together with a lead and tin alloy. In soldering, the wires should be spliced together with a crimp. The less solder separating the wire strands, the stronger the joint. • SOLDER Solder is a mixture of lead and tin plus traces of other substances. Flux core wire solder (wire solderwith a hollow center filled with flux) is recommended for electrical splices. • SOLDERING FLUX Soldering heats the wires. In so doing, it accelerates oxidization, leaving a thin film of oxide on the wires that tends to reject solder. Flux removes this oxide and prevents further oxidation during the soldering process. Rosin or resin-type flux must be used for all electrical work. The residue will not cause corrosion, nor will it conduct electricity. • SOLDERING IRONS The soldering iron should be the right size for the job. An iron that is too small will require excessive time to heat the work and may never heat it properly. A low- wattage (25-100 W) iron works best for wiring repairs. • CLEANING WORK All traces of paint, rust, grease, and scale must be removed. Good soldering requires clean, tight splices. WIRE, TERMINAL AND CONNECTOR REPAIR Page 5 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  46. 46. • TINNING THE IRON The soldering iron tip is made of copper. Through the solvent action of solder and prolonged heating, it will pit and corrode. An oxidized or corroded tip will not satisfactorily transfer heat from the iron to the work. It should be cleaned and tinned. Use a file and dress the tip down to the bare copper. File the surfaces smooth and flat. Then, plug the iron in. When the tip color begins to change to brown and light purple, dip the tip in and out of a can of soldering flux (rosin type). Quickly apply rosin core wire solder to all surfaces. The iron must be at operating temperature to tin properly. When the iron is at the proper temperature, solder will melt quickly and flow freely. Never try to solder until the iron is properly tinned. • SOLDERING WIRE SPLICES Apply the tip flat against the splice. Apply rosin-core wire solder to the flat of the iron where it contacts the splice. As the wire heats, the solder will flow through the splice. • RULES FOR GOOD SOLDERING 1. Clean wires. 2. Wires should be crimped together. 3. Iron must be the right size and must be hot. 4. Iron tip must be tinned. 5. Apply full surface of soldering tip to the splice. 6. Heat wires until solder flows readily. 7. Use rosin-core solder. 8. Apply enough solder to form a secure splice. 9. Do not move splice until solder sets. 10. Place hot iron in a stand or on a protective pad. 11. Unplug iron as soon as you are finished. WIRE, TERMINAL AND CONNECTOR REPAIR Page 6 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  47. 47. Step 1. Identify the connector and terminal type. 1. Replacing Terminals a. Identify the connector name, position of the locking clips, the un-locking direction and terminal type from the pictures provided on the charts. Step 2. Remove the terminal from the connector. 1. Disengage the secondary locking device or terminal retainer. a. Locking device must be disengaged before the terminal locking clip can be released and the terminal removed from the connector. b. Use a miniature screwdriver or the terminal pick to unlock the secondary locking device. 2. Determine the primary locking system from the charts. a. Lock located on terminal b. Lock located on connector c. Type of tool needed to unlock d. Method of entry and operation WIRE, TERMINAL AND CONNECTOR REPAIR Page 7 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  48. 48. 3. Remove terminal from connector by releasing the locking clip. a. Push the terminal gently into the connector and hold it in this position. b. Insert the terminal pick into the connector in the direction shown in the chart. c. Move the locking clip to the un-lock position and hold it there. NOTE: Do not apply excessive force to the terminal. Do not pry on the terminal with the pick. d. Carefully withdraw the terminal from the connector by pulling the lead toward the rear of the connector. NOTE: Do not use too much force. If the terminal does not come out easily, repeat steps (a.) through (d.). 4. Measure "nominal" size of the wire lead by placing a measuring device, such as a micrometer or Vernier Caliper, across the diameter of the insulation on the lead and taking a reading. 5. Select the correct replacement terminal, with lead, from the repair kit. WIRE, TERMINAL AND CONNECTOR REPAIR Page 8 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  49. 49. 6. Cut the old terminal from the harness. a. Use the new wire lead as a guide for proper length. NOTE: If the length of wire removed is not approximately the same length as the new piece, the following problems may develop: Too short - tension on the terminal, splice, or the connector, causing an open circuit. Too long - excessive wire near the connector, may get pinched or abraded, causing a short circuit. NOTE: If the connector is of a waterproof type, the rubber plug may be reused. 7. Strip insulation from wire on the harness and replacement terminal lead. a. Strip length should be approximately 8 to 10 mm (3/8 in.). NOTE: Strip carefully to avoid nicking or cutting any of the strands of wire. NOTE: If heat shrink tube is to be used, it must be installed at this time, sliding it over the end of one wire to be spliced. (See Step 3, 4. B. 1. for instructions on how to use heat shrink tube.) NOTE: If the connector is a waterproof type, the rubber plug should be installed on the terminal end at this time. WIRE, TERMINAL AND CONNECTOR REPAIR Page 9 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  50. 50. 1. Select correct size of splice from the repair kit. a. Size is based on the nominal size of the wire (three sizes are available). Part Number Wire Size Small 00204-34130 16-22 AWG 1.0 - 0.2 mm Medium 00204-34137 14-16 AWG 2.0 - 1.0 mm Large 00204-34138 10 - 12 AWG 5.0 - 3.0 mm 2. Crimp the replacement terminal lead to the harness lead. a. Insert the stripped ends of both the replacement lead and the harness lead into the splice, overlapping the wires inside the splice. NOTE: Do not place insulation in the splice, only stripped wire. b. Do not use position marked "INS". The crimping tool has positions marked for insulated splices (marked "INS") that should not be used, as they will not crimp the splice tightly onto the wires. c. Use only position marked "NON INS". 1. With the center of the splice correctly placed between the crimping jaws, squeeze the crimping tool together until the contact points of the crimper come together. NOTE: Make sure the wires and the splice are still in the proper position before closing the crimping tool ends. Use steady pressure in making the crimp. 2. Make certain that the splice is crimped lightly. WIRE, TERMINAL AND CONNECTOR REPAIR Page 10 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  51. 51. 3. Solder the completed splice using only rosin core solder. a. Wires and splices must be clean. b. A good mechanical joint must exist, because the solder will not hold the joint together. c. Heat the joint with the soldering iron until the solder melts when pressed onto the joint. d. Slowly press the solder into the hot splice on one end until it flows into the joint and out the other end of the splice. NOTE: Do not use more solder than necessary to achieve a good connection. There should not be a "glob" of solder on the splice. e. When enough solder has been applied, remove the solder from the joint and then remove the soldering iron. 4. Insulate the soldered splice using one of the following methods: a. Silicon tape (provided in the wire repair kit) 1. Cut a piece of tape from the roll approximately 25 mm (1 in.) long. 2. Remove the clear wrapper from the tape. NOTE: The tape will not feel "sticky" on either side. 3. Place one end of the tape on the wire and wrap the tape tightly around the wire. You should cover one-half of the previous wrap each time you make a complete turn around the wire. (When stretched, this tape will adhere to itself.) 4. When completed, the splice should be completely covered with the tape and the tape should stay in place. If both of these conditions are not met, remove the tape and repeat steps 1 through 4. NOTE: If the splice is in the engine compartment or under the floor, or in an area where there might be abrasion on the spliced area, cover the silicon tape with vinyl tape. WIRE, TERMINAL AND CONNECTOR REPAIR Page 11 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  52. 52. b. Heat shrink tube (provided in the wire repair kit) 1. Cut a piece of the heat shrink tube that is slightly longer than the splice, and slightly larger in diameter than the splice. 2. Slide the tube over the end of one wire to be spliced. (THIS STEP MUST BE DONE PRIOR TO JOINING THE WIRES TOGETHER!) 3. Center the tube over the soldered splice. 4. Using a source of heat, such as a heat gun, gently heat the tubing until it has shrunk tightly around the splice. NOTE: Do not continue heating the tubing after it has shrunk around the splice. It will only shrink a certain amount, and then stop. It will not continue to shrink as long as you hold heat to it, so be careful not to melt the insulation on the adjoining wires by trying to get the tubing to shrink further. Step 4. Install the terminal into the connector. 1. If reusing a terminal, check that the locking clip is still in good condition and in the proper position. a. If it is on the terminal and not in the proper position, use the terminal pick to gently bend the locking clip back to the original shape. b. Check that the other parts of the terminal are in their original shape. WIRE, TERMINAL AND CONNECTOR REPAIR Page 12 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  53. 53. 2. Push the terminal into the connector until you hear a "click". NOTE: Not all terminals will give an audible "click". a. When properly installed, pulling gently on the wire lead will prove the terminal is locked in the connector. 3. Close terminal retainer or secondary locking device. a. If the connector is fitted with a terminal retainer, or a secondary locking device, return it to the lock position. 4. Secure the repaired wire to the harness. a. If the wire is not in the conduit, or secured by other means, wrap vinyl tape around the bundle to keep it together with the other wires. WIRE, TERMINAL AND CONNECTOR REPAIR Page 13 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  54. 54. WIRE, TERMINAL AND CONNECTOR REPAIR ASSIGNMENT NAME: 1. Explain which type of wire is used when current flow is high. 2. Explain what is mean by system polarity and how is it used today. 3. Explain how the colors of the wire insulation are used and give an example. 4. Explain how wire is sized, different sizing systems, and provide examples. 5. Name the correct type of solder used for electrical repair repair and why 6. Outline the procedure for “Tinning an Iron”. 7. List the rules for good soldering. 8. Outline in detail the correct procedure for splicing a new wire end on. 9. When and why is a heat gun used?
  55. 55. General The battery is the primary "source" of electrical energy on Toyota vehicles. It stores chemicals, not electricity. Two different types of lead in an acid mixture react to produce an electrical pressure. This electrochemical reaction changes chemical energy to electrical energy. Battery Functions 1. ENGINE OFF: Battery energy is used to operate the lighting and accessory systems. 2. ENGINE STARTING: Battery energy is used to operate the starter motor and to provide current for the ignition system during cranking. 3. ENGINE RUNNING: Battery energy may be needed when the vehicle's electrical load requirements exceed the supply from the charging system. In addition, the battery also serves as a voltage stabilizer, or large filter, by absorbing abnormal, transient voltages in the vehicle's electrical system. Without this protection, certain electrical or electronic components could be damaged by these high voltages. Battery Types 1. PRIMARY CELL: The chemical reaction totally destroys one of the metals after a period of time. Small batteries for flashlights and radios are primary cells. 2. SECONDARY CELLS: The metals and acid mixture change as the battery supplies voltage. The metals become similar, the acid strength weakens. This is called discharging. By applying current to the battery in the opposite direction, the battery materials can be restored. This is called charging. Automotive lead-acid batteries are secondary cells. 3. WET-CHARGED: The lead-acid battery is filled with electrolyte and charged when it is built. During storage, a slow chemical reaction will cause self- discharge. Periodic charging is required. For Toyota batteries, this is every 5 to 7 months. 4. DRY-CHARGED: The battery is built, charged, washed and dried, sealed, and shipped without electrolyte. It can be stored for 12 to .18 months. When put into use, it requires adding electrolyte and charging. 5. LOW-MAINTENANCE: Most batteries for Toyota vehicles are considered low-maintenance batteries. Such batteries are built to reduce internal heat and water loss. The addition of water should only be required every 15,000 miles or so. BATTERIES Page 1 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  56. 56. Construction 1. CASE: Container which holds and protects all battery components and electrolyte, separates cells, and provides space at the bottom for sediment (active materials washed off plates). Translucent plastic cases allow checking electrolyte level without removing vent caps. 2. COVER: Permanently sealed to the top of the case; provides outlets for terminal posts, vent holes for venting of gases and for battery maintenance (checking electrolyte, adding water). 3. PLATES: Positive and negative plates have a grid framework of antimony and lead alloy. Active material is pasted to the grid ... brown-colored lead dioxide (Pb02) on positive plates, gray- colored sponge lead (Pb) on negative plates. The number and size of the plates determine current capability ... batteries with large plates or many plates produce more current than batteries with small plates or few plates. 4. SEPARATORS: Thin, porous insulators (woven glass or plastic envelopes) are placed between positive and negative plates. They allow passage of electrolyte, yet prevent the plates from touching and shorting out. 5. CELLS: An assembly of connected positive and negative plates with separators in between is called a cell or element. When immersed in electrolyte, a cell produces about 2.1 volts (regardless of the number or size of plates). Battery cells are connected in series, so the number of cells determines the battery voltage. A "1 2 - volt" battery has six cells. 6. CELL CONNECTORS: Heavy, cast alloy metal straps are welded to the negative terminal of one cell and the positive terminal of the adjoining cell until all six cells are connected in series. 7. CELL PARTITIONS: Part of the case, the partitions separate each cell. 8. TERMINAL POSTS: Positive and negative posts (terminals) on the case top have thick, heavy cables connected to them. These cables connect the battery to the vehicle's electrical system (positive) and to ground (negative). 9. VENT CAPS: Types include individual filler plugs, strip-type, or box-type. They allow controlled release of hydrogen gas during charging (vehicle operation). Removed, they permit checking electrolyte and, if necessary, adding water. 10. ELECTROLYTE: A mixture of sulfuric acid (H2SO4) and water (H2O). It reacts chemically with the active materials in the plates to create an electrical pressure (voltage). And, it conducts the electrical current produced by that pressure from plate to plate. A fully charged battery will have about 36% acid and 64% water. BATTERIES Page 2 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  57. 57. CELL THEORY A lead-acid cell works by a simple principle: when two different metals are immersed in an acid solution, a chemical reaction creates an electrical pressure. One metal is brown-colored lead dioxide (Pb02). It has a positive electrical charge. The other metal is gray colored sponge lead (Pb). It has a negative electrical charge. The acid solution is a mixture of sulfuric acid (H2SO4) and water (H20). It is called electrolyte. If a conductor and a load are connected between the two metals, current will flow. This discharging will continue until the metals become alike and the acid is used up. The action can be reversed by sending current into the cell in the opposite direction. This charging will continue until the cell materials are restored to their original condition. BATTERIES Page 3 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  58. 58. ELECTROCHEMICAL REACTION A lead-acid storage battery can be partially discharged and recharged many times. There are four stages in this discharging/charging cycle. 1. CHARGED: A fully charged battery contains a negative plate of sponge lead (Pb), a positive plate of lead dioxide (Pb02), and electrolyte of sulfuric acid (H2SO4) and water (H20). 2. DISCHARGING: As the battery is discharging, the electrolyte becomes diluted and the plates become sulfated. The electrolyte divides into hydrogen (H2) and sulfate(S04) . The hydrogen (H2) combines with oxygen (0) from the positive plate to form more water (H20). The sulfate combines with the lead (Pb) in both plates to form lead sulfate (PbS04) 3. DISCHARGED: In a fully discharged battery, both plates are covered with lead sulfate (PbSO4) and the electrolyte is diluted to mostly water (H2O). 4. CHARGING: During charging, the chemical action is reversed. Sulfate (S04) leaves the plates and combines with hydrogen (H2) to become sulfuric acid (H2SO4). Free oxygen (02) combines with lead (Pb) on the positive plate to form lead dioxide (Pb02). Gassing occurs as the battery nears full charge, and hydrogen bubbles out at the negative plates, oxygen at the positive. BATTERIES Page 4 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  59. 59. Capacity Ratings The battery must be capable of cranking the engine and providing adequate reserve capacity. Its capacity is the amount of electrical energy the battery can deliver when fully charged. Capacity is determined by the size and number of plates, the number of cells, and the strength and volume of electrolyte. The most commonly used ratings are: • Cold Cranking Amperes (CCA) • Reserve Capacity (RC) • Amp-Hours (AH) • Power (Watts) COLD-CRANKING AMPERES (CCA) The battery's primary function is to provide energy to crank the engine during starting. This requires a large discharge in a short time. The CCA Rating specifies, in amperes, the discharge load a fully charged battery at 0˚F (-1 7.8˚C) can deliver for 30 seconds while maintaining a voltage of at least 1.2 volts per cell (7.2 volts total for a 12-volt battery). Batteries used on various Toyota vehicles have CCA ratings ranging from 350 to 560 amps. RESERVE CAPACITY (RC) The battery must provide emergency energy for ignition, lights, and accessories if the vehicle's charging system fails. This requires adequate capacity at normal temperatures for a certain amount of time. The RC Rating specifies, in minutes, the length of time a fully charged battery at 80˚F (26.7'C) can be discharged at 25 amps while maintaining a voltage of at least 1.75 volts per cell (10.5 volts total for a 12-volt battery). Batteries used on various Toyota vehicles have RC ratings ranging from 55 to 115 minutes. AMP-HOURS (AH) The battery must maintain active materials on its plates and adequate lasting power under light-load conditions. This method of rating batteries is also called the 20-hour discharge rating. Original equipment batteries are rated in amp-hours. The ratings of these batteries are listed in the parts microfiche. The Amp-Hour Rating specifies, in amphours, the current the battery can provide for 20 hours at 80˚F (26.7˚C) while maintaining a voltage of at least 1.75 volts per cell (10.5 volts total for a 12- volt battery). For example, a battery that can deliver 4 amps for 20 hours is rated at 80 amp-hours (4 x 20 = 80). Batteries used on various Toyota vehicles have AH ratings ranging from 40 to 80 amp-hours. POWER (WATTS) The battery's available cranking power may also be measured in watts. The Power Rating, in watts, is determined by multiplying the current available by the battery voltage at 0˚F (-1 7.8˚C). Batteries used on various Toyota vehicles have power ratings ranging from 2000 to 4000 watts. BATTERIES Page 5 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  60. 60. FACTORS AFFECTING CHARGING Five factors affect battery charging by increasing its internal resistance and CEMF (counter-electromotive force produced by the electrochemical reaction): 1. TEMPERATURE: As the temperature decreases the electrolyte resists charging. A cold battery will take more time to charge; a warm battery, less time. Never attempt to charge a frozen battery. 2. STATE-OF-CHARGE: The condition of the battery's active materials will affect charging. A battery that is severely discharged will have hard sulfate crystals on its plates. The vehicle's charging system may charge at too high of a rate to remove such sulfates. 3. PLATE AREA: Small plates are charged faster than large plates. When sulfation covers most of the plate area, the charging system may not be able to restore the battery. 4. IMPURITIES: Dirt and other impurities in the electrolyte increase charging difficulty. 5. GASSING: Hydrogen and oxygen bubbles form at the plates during charging. As these bubble out, they wash away active material, cause water loss, and increase charging difficulty. BATTERIES Page 6 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  61. 61. BATTERIES Page 7 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  62. 62. Diagnosis and Testing All batteries require routine maintenance to identify and correct problems caused by physical abuse and low electrolyte levels. A visual inspection can identify such physical problems. A state-of-charge test checks the electrolyte strength. And, electrical testing identifies overcharging or undercharging problems. These tests include a capacity, or heavy- load, test. SAFETY FIRST! When testing or servicing a battery, safety should be your first consideration. The electrolyte contains sulfuric acid. It can eat your clothes. It can burn your skin. It can blind you if it gets in your eyes. It can also ruin a car's finish or upholstery. If electrolyte is splashed on your skin or in your eyes, wash it away immediately with large amounts of water. If electrolyte is spilled on the car, wash it away with a solution of baking soda and water. When a battery is being charged, either by the charging system or by a separate charger, gassing will occur. Hydrogen gas is explosive. Any flame or spark can ignite it. If the flame travels into the cells, the battery may explode. Safety precautions include: • Wear gloves and safety glasses. • Remove rings, watches, other jewelry. • Never use spark-producing tools near a battery. • Never lay tools on the battery. • When removing cables, always remove the ground cable first. • When connecting cables, always connect the ground cable last. • Do not use the battery ground terminal when checking for ignition spark. • Be careful not to get electrolyte in your eyes or on your skin, the car finish, or your clothing. • If you have to mix battery electrolyte, pour the acid into the water - not the water into the acid. • Always follow the recommended procedures for battery testing and charging and for jump starting an engine. CARE OF ELECTRONICS Disconnecting the battery will erase the memory on electronic devices. Write down trouble codes and programmed settings before disconnecting the battery. Also, to prevent damage to electronic components: • Never disconnect the battery with the ignition ON. • Never use an electric welder without the battery cables disconnected. • Never reverse battery polarity. BATTERIES Page 8 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  63. 63. VISUAL INSPECTION Battery service should begin with a thorough visual inspection. This may reveal simple, easily corrected problems, or problems that might require battery replacement. 1 . Check for cracks in the battery case and for broken terminals. Either may allow electrolyte leakage. The battery must be replaced. 2. Check for cracked or broken cables or connections. Replace, as needed. 3. Check for corrosion on terminals and dirt or acid on the case top. Clean the terminals and case top with a mixture of water and baking soda or ammonia. A wire brush is needed for heavy corrosion on the terminals. 4. Check for a loose battery hold-down and loose cable connections. Tighten, as needed. 5. Check the level of electrolyte. The level can be viewed through the translucent plastic case or by removing the vent caps and looking directly into each cell. The proper level is 1/2" above the separators. If necessary, add distilled water to each low cell. Avoid overfilling. When water is added, always charge the battery to make sure the water and acid mix. 6. Check for cloudy or discolored electrolyte caused by overcharging or vibration. This could cause high self discharge. The problem should be corrected and the battery replaced. 7. Check the condition of plates and separators. Plates should alternate dark (+) and light (-). If all are light, severe undercharging is indicated. Cracked separators may allow shorts. The battery should be replaced. An undercharging problem should be corrected. BATTERIES Page 9 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  64. 64. 8. Check the tension and condition of the alternator drive belt. A loose belt must be tightened. It will prevent proper charging. A belt too tight will reduce alternator life. It should be loosened to specs. A frayed or glazed belt will fail during operation. Replace it. NOTE: Approved Equipment tension gauge: Nippondenso, BTG-20 (SST) Borroughs BT-33-73F 9. Check for battery drain or parasitic loads using an ammeter. Connect the ammeter in series between the battery negative terminal and ground cable connector. Toyota vehicles typically show less than .020 amp of current to maintain electronic memories ... a reading of more than .035 amp is unacceptable. If the ammeter reads more than .035 amp, locate and correct the cause of excessive battery drain. 10. Check for battery discharge across the top of the battery using a voltmeter. Select the low voltage scale on the meter, connect the negative (black) test lead to the battery's negative post, and connect the positive (red) test lead to the top of the battery case. If the meter reading is more than 0.5 volt, clean the case top using a solution of baking soda and water. BATTERIES Page 10 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
  65. 65. STATE-OF-CHARGE TEST The state-of-charge test checks the battery's chemical condition. One method uses a hydrometer to measure the specific gravity of the electrolyte. Another method uses a digital voltmeter to check the battery's open circuit voltage and, for a general indication of the battery's condition, check the indicator eye (if the battery has one) or check the headlamp brightness during starting. Specific Gravity Specific gravity means exact weight. The hydrometer compares the exact weight of electrolyte with that of water. Strong electrolyte in a charged battery is heavier than weak electrolyte in a discharged battery. By weight, the electrolyte in a fully charged battery is about 36% acid and 64% water. The specific gravity of water is 1.000. The acid is 1.835 times heavier than water, so its specific gravity is 1.835. The electrolyte mixture of water and acid has a specific gravity of 1.270 is usually stated as "twelve and seventy." By measuring the specific gravity of the electrolyte, you can tell if the battery is fully charged, requires charging, or must be replaced. It can tell you if the battery is charged enough for the capacity, or heavy- load test. TEST PROCEDURE: The following steps outline a typical procedure for performing a state-of-charge test: 1 . Remove vent caps or covers from the battery cells. 2. Squeeze the hydrometer bulb and insert the pickup tube into the cell closest to the battery's positive (+) terminal. 3. Slowly release the bulb to draw in only enough electrolyte to cause the float to rise. Do not remove the tube from the cell. 4. Read the specific gravity indicated on the float. Be sure the float is drifting free, not in contact with the sides of top of the barrel. Bend down to read the hydrometer a eye level. Disregard the slight curvature of liquid on the float. 5. Read the temperature of the electrolyte. 6. Record your readings and repeat the procedure for the remaining cells. TEMPERATURE CORRECTION: The specific gravity changes with temperature. Heat thins the liquid, and lowers the specific gravity. Cold thickens the liquid, and raises the specific gravity. Hydrometers are accurate at 80-F (26.7˚C). If the electrolyte is at any other temperature, the hydrometer readings must be adjusted. Most hydrometers have a built-in thermometer and conversion chart. Refer to the temperature correction chart. For each 1 O˚F (5.5˚C) above 80˚F (26.7˚C), ADD 0.004 to your reading. BATTERIES Page 11 © Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.