Alternator: Testing and Inspection
INSPECTION1. INSPECT GENERATOR ROTOR ASSEMBLY
a. Check the resistance.
1. Measure the resistance between the slip rings.
Standard resistance: 2.1 to 2.5 ohms at 20° (68 °F)
If the result is not as specified, replace the generator rotor assembly.
2. Measure the resistance between the slip ring and rotor core.
Standard resistance: 10 kohms or higher
If the result is not as specified, replace the generator rotor assembly.
b. Check the slip ring diameter.
1. Using a vernier caliper, measure the slip ring diameter.
Standard diameter: 14.2 to 14.4 mm (0.559 to 0.567 in.)
Minimum diameter: 14.0 mm (0.551 in.)
If the result is not as specified, replace the generator rotor assembly.
c. Check the bearing condition.
1. Check that the bearing is not rough or worn.
OK:The bearing rotates smoothly.
If the result is not as specified, replace the generator rotor assembly.
2. INSPECT DRIVE END FRAME
a. Check that the front bearing condition.
OK: The bearing rotates smoothly.
If the result is nit as specified, replace the front bearing.
3. INSPECT GENERATOR BRUSH HOLDER ASSEMBLY
a. Using a vernier caliper, measure the brush length.
Standard length: 9.5 to 11.5 mm (0.374 to 0.453 in.)
Minimum length: 4.5 mm (0.177 in.)
If the brush length is less than the minimum, replace the generator brush holder assembly.