ALTERNATOR
OVERHAUL
AUTOMOTIVE TECHNOLOGY
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
DISASSEMBLY
Part
number
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•
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•
Mark frames for correct reassembly
Note spacers placement
Identify Alternator by Part Number
Note Terminal Condition & orientation
INSPECTION OF “COM” END
HOUSING
• Bearing
condition
• Stator windings
• Pulley condition
• Brush wear
• Internal Wiring
Connections
• Component
external damage
INSPECTION OF DRIVE END
HOUSING (FRAME)
• Bearing race housings
• Frame Condition
– Cracks
– Wear
– Stripped threads
• Mounting boss
condition
• Rotor slip ring
condition
• Rotor Windings
external condition
• Shaft condition
• Cooling Fan
condition
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.
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
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
DIODE TESTING
Note: Diodes can be checked on
car with Sun VAT 40
• 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!!!
TEST STATOR FOR
CONTINUITY
• Check Stator for
Continuity
between phases of
windings
• Usually check
resistance of
windings
• Must be same
resistance
TEST STATOR FOR
• Make sure GROUNDS
Stator windings
are not
grounded to
frame!
• Inspect
windings for
worn spots on
windings.
• Check
looseness
DELCO REMY 25SI AND 30SI
ALTERNATORS
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
LOTS OF WIRE
CONNECTIONS!!!
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
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
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
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.
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