Alternator: Testing and Inspection

GENERATOR INSPECTION AND REPAIR







Rotor
1. INSPECT ROTOR FOR OPEN CIRCUIT
Using an ohmmeter, check that there is continuity between the slip rings.

Standard resistance:
At 20° C (68° F): 2.1 - 2.5 Ohms

If there is no continuity, replace the rotor.







2. INSPECT ROTOR FOR GROUND
Using an ohmmeter, check that there is no continuity between the slip ring and rotor.

If there is continuity, replace the rotor.







3. INSPECT SLIP RINGS
a. Check that the slip rings are not rough or scored. If rough or scored, replace the rotor.
b. Using vernier calipers, measure the slip ring diameters.

Standard diameter:
14.2 - 14.4 mm (0.559 - 0.567 in.)
Minimum diameter:
12.8 mm (0.504 in.)

If the diameter is less than the minimum, replace the rotor.








Stator (Drive End Frame)
1. INSPECT STATOR FOR OPEN CIRCUIT
Using an ohmmeter, check that there is continuity between the coil leads.

If there is no continuity, replace the drive end frame assembly.







2. INSPECT STATOR FOR GROUND
Using an ohmmeter, check that there is no continuity between the coil leads and drive end frame.

If there is continuity, replace the drive end frame assembly.








Brushes
1. INSPECT EXPOSED BRUSH LENGTH
Using a scale, measure the exposed brush length.

Standard exposed length:
9.5 - 11.5 mm (0.374 - 0.452 in.)
Minimum exposed length:
1.5 mm (0.059 in.)

If the exposed length is less than the minimum, replace the brushes.

2. IF NECESSARY, REPLACE BRUSHES



Brushes







REPLACEMENT
1. Unsolder and remove the brush and spring.
2. Run the wire of the brush through the hole in the brush holder, and insert the spring and brush into the brush holder.







3. Solder the brush wire to the brush holder at the exposed length.

Exposed length:
9.5 - 11.5 mm (0.374 - 0.452 in.)

4. Check that the brush moves smoothly in the brush holder.
5. Cut off the excess wire.
6. Apply insulation paint to the soldered point.








Rectifiers (Rectifier Holder)
1. INSPECT POSITIVE RECTIFIER
a. Using an ohmmeter, connect one tester probe to the positive (+) terminal and the other to each rectifier terminal.
b. Reverse the polarity of the tester probes and repeat Step (a).
c. Check that one shows continuity and the other shows no continuity.

If continuity is not as specified, replace the rectifier holder.

2. INSPECT NEGATIVE RECTIFIER







a. Using an ohmmeter, connect one tester probe to each negative (-) terminal and the other to each rectifier terminal.
b. Reverse the polarity of the tester probes and repeat step (a).
c. Check that one shows continuity and the other shows no continuity.

If continuity is not as specified, replace the rectifier holder.



Bearings
1. INSPECT FRONT BEARING
Check that the bearing is not rough or worn.

2. IF NECESSARY, REPLACE FRONT BEARING

3. INSPECT REAR BEARING
Check that the bearing is not rough or worn.

4. IF NECESSARY, REPLACE REAR BEARING


Bearings
REPLACEMENT FRONT BEARING
1. Remove the 4 screws and bearing retainer.







2. Using a press and socket wrench, press out the front bearing.
SST 09950-60010 (09951-00260, 09952-06010)







3. Using SST and a press, press the front bearing into the drive end frame.
SST 09950-60010 (09951-00500)

4. Install the bearing retainer with the 4 screws.

REPLACEMENT REAR BEARING







1. Using SST, remove the bearing cover and bearing.
SST 09820-00021

2. Remove the bearing cover (inside).







3. Place the bearing cover (inside) on the rotor.







4. Using SST and a press, press in a new bearing and the bearing cover.
SST 09820-00030







5. Using SST, push in the bearing cover (outside).
SST 09285-76010







6. Place the generator washer on the rotor.