(a) Using a vernier caliper, measure the length of the exposed brushes.

Standard Exposed Brush Length:

9.5 to 11.5 mm (0.374 to 0.453 in.)

Minimum Exposed Brush Length:

4.5 mm (0.177 in.)

If the brush length is less than the minimum, replace the generator brush holder assembly.

(a) Check the generator rotor assembly for an open circuit.

(1) Measure the resistance according to the value(s) in the table below.

Standard Resistance:

If the result is not as specified, replace the generator rotor assembly.

(b) Check the generator rotor assembly for a short to ground.

(1) Measure the resistance according to the value(s) in the table below.

Standard Resistance:

If the result is not as specified, replace the generator rotor assembly.

(c) Check that the generator rotor bearing is not rough or worn and that it rotates smoothly.

If the generator rotor bearing is rough or worn, or does not rotate smoothly, replace the generator rotor assembly.

(d) Check the slip ring.

(1) Check that the slip rings are not rough or scored.

If the slip rings are rough or scored, replace the generator rotor assembly.

(2) Using a vernier caliper, measure the slip ring diameter.

Standard Diameter:

14.2 to 14.8 mm (0.559 to 0.583 in.)

Minimum Diameter:

14.0 mm (0.551 in.)

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

(a) Check that the generator drive end frame bearing is not rough or worn and that it rotates smoothly.

If the generator drive end frame bearing is rough or worn, or does not rotate smoothly, replace the generator drive end frame bearing.