alternator principles and construction

1. ALTERNATOR
OVERHAUL
AUTOMOTIVE TECHNOLOGY

2. BEFORE YOU REMOVE
ALTERNATOR
• Pay attention to how
wires are connected
• Pay attention to
Alternator oreintation
• Disconnect Battery!!
• Check Belt tension
and condition
• Check wiring
condition

3. DISASSEMBLY
Part
number
• Mark frames for correct reassembly
• Note spacers placement
• Identify Alternator by Part Number
• Note Terminal Condition & orientation

4. INSPECTION OF “COM” END
HOUSING
• Bearing
condition
• Stator windings
• Pulley condition
• Brush wear
• Internal Wiring
Connections
• Component
external damage

5. INSPECTION OF DRIVE END
HOUSING (FRAME)
• Bearing race housings
• Frame Condition
– Cracks
– Wear
– Stripped threads
• Mounting boss
condition

6. • Rotor slip ring
condition
• Rotor Windings
external condition
• Shaft condition
• Cooling Fan
condition

7. TESTING ROTOR FIELD COIL
• Rotor resistance
– GM 2.4 to 3.5 ohms
– Ford 3.0 to 5.5 ohms
– Chrysler 3.0 to 6.0 ohms
• Some shop manuals give
rotor specifications in
amps.

8. ROTOR TESTING FOR
GROUNDED SLIP RINGS
• Inspect rotor lead
soldering area
• Test rotor for
Grounds to shaft
• Can use
ohmmeter
• Can use 110 Volt
continuity tester

9. ROTOR TESTING FOR
GROUND TO ROTOR
FRAME
• Test rotor for
grounds to rotor
frame (open circuit
cats claw)
• Should be
• Inspect cats claw
for signs of
rubbing on stator

10. DIODE TESTING
• Check Positive diodes
for one way operation
by switching leads.
• Can test with diode
check function of
DVOM
• Can check with 110V
diode tester tool.
• Check Negative
Diodes also
• Must only get
Note: Diodes can be checked on
continuity one way!!!
car with Sun VAT 40

11. TEST STATOR FOR
CONTINUITY
• Check Stator for
Continuity
between phases of
windings
• Usually check
resistance of
windings
• Must be same
resistance

12. TEST STATOR FOR
• Make sure GROUNDS
Stator windings
are not
grounded to
frame!
• Inspect
windings for
worn spots on
windings.
• Check
looseness

13. DELCO REMY 25SI AND
30SI ALTERNATORS

14. ADVANTAGES OF HEAVY
DUTY 25-SI ALTERNATOR
• BRUSHLESS - ROTOR WORKS ON
PERMANENT MAGNETISM
• BELT OR GEAR DRIVEN
• 12V, 24V, 32V
• 85 AMP TO 300 AMP CAPABILITY
• ELECTRONIC REGULATOR
• 12V - 24V COMBINATION OUTPUT
• SOME ARE OIL COOLED

15. LOTS OF WIRE
CONNECTIONS!!!

16. 25SI ROTOR
• Rotor doesn’t spin in
this alternator
• Stator is stationary
also
• Inspect Rotor and
stator for interference
• Check stator and rotor
as any other alternator

17. 25SI ROTOR HOUSING
• Inspect for
interference
• Inspect bearing races
• Remove bearing race
with bearing splitter
• Inspect D.E. Bearing
• Inspect C.E. Bearing
• Inspect Housing
threads and condition

18. REPAIR
• Clean components
– OK to clean in solvent but make sure dry
• Replace Bearings
– Don’t spin bearings
– Inspect races closely
– Use proper procedures to replace and remove
bearings.
• Replace Brushes and Springs
• Replace other faulty components

19. REASSEMBLY
• Proper Torque
• Paint Housing if necessary
• Use Lock Tight on H.D. Alternators
• Make sure there is no tension on wiring
• Make sure connections are tight!!
• Always retest output after Overhaul.

20. Final Bench Testing
• Check amperage output
– Look up specifications In book
– Listen for abnormal noises
• Check internal regulator operation
– Make sure cutoff voltage is correct.
• Test Light/Indicator circuits also.
• Reinstall on Vehicle