Generator Bench Tests

If generator component tests have isolated a concern in the generator, remove it from the vehicle for bench testing and service or replace as necessary.

Stator and Coil Grounded Test
1. Inspect the stator and coil laminations closely for signs of overheating. A burnt spot usually indicates a shorted coil winding. In this case the stator and coil should be replaced.







2. Use 73 Digital Multimeter 105-R0051 or equivalent to check for continuity between the three coil leads and the stator. If continuity exists, a grounded coil is indicated. In this case the stator and coil should be replaced.

Stator and Coil Open Test







Use 73 Digital Multimeter 105-R0051 or equivalent to check for continuity between the coil leads. No continuity between any two leads indicates an open winding. In this case the stator and coil should be replaced.

Generator Rotor Open or Short Test
1. Use Rotunda 73 Digital Multimeter 105-R0051 or equivalent to measure the resistance at the slip rings.







2. The reading should be 2.5 to 3.6 ohms. If not, replace the generator rotor.







3. To test for a shorted field coil, check continuity between each slip ring and the rotor core. Replace the generator rotor if continuity exists, indicating a shorted coil.
4. Use fine emery paper to clean the slip rings if they are grooved or appear dark.

Brushes







1. Replace the generator brushes if they are worn down to the 8 mm (0.315 in) wear limit.
2. If it is necessary to replace the generator brushes.






3. Brush springs may be checked by using a spring pressure gauge to push the brush into the brush holder until the tip of the brush projects 2 mm (0.080 inch). Read the force at this time. For a brush, the force should be 3.14 to 4.31N (11.3-15.5 oz). The minimum force for any brush is 1.57-2.35N (5.65-8.47 oz). If the spring force is less than the minimum force range, replace the generator brush.

Rectifier







1. Use 73 Digital Multimeter 105-R0051 or equivalent in the diode test mode to check for continuity between the following terminals of the rectifier. If an analog meter is used, the test may give false readings.







2. If the rectifier fails any of the above continuity checks, replace the rectifier.