Alternator: Testing and Inspection

INSPECTION




1. 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.




2. INSPECT GENERATOR ROTOR ASSEMBLY
a. Check the resistance.
1. Measure the resistance between the slip rings.
Standard resistance: 2.3 to 2.7 ohm at 20 degrees C (68 degrees 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: 1Mohm 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 mm (0.551 in.)
If the diameter is less than the minimum, replace the generator rotor assembly.




c. Check the appearance.
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.




3. INSPECT GENERATOR DRIVE END FRAME BEARING
a. Check that the bearing is not rough or worn.
Standard:The bearing rotates smoothly.
If the bearing does not rotate smoothly, replace the generator assembly.