1. AUTOMOTIVE TECHNOLOGY
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 Disassembly Mark frames for correct reassembly
Part
number
Disassembly
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 VISUAL INSPECTION
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
Check that commutator!

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 continuity one way!!!
Note: Diodes can be checked on 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 GROUNDS
Make sure 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 Replace Bearings Replace Brushes and Springs
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