Generator On-Vehicle Tests

Troubleshooting or diagnosis is required before actual service can be made in the electrical system. Even where an obvious condition makes replacement of a component necessary, find out why the component failed. When a condition is diagnosed correctly, unnecessary service is prevented, the time the vehicle is out of service will be decreased, and the condition will be properly corrected the first time.

NOTE: Refer to the Rotunda Battery and Starter Tester Operator's Manual for complete directions on checking out the charging system.

In order to check the charging system, the use of Rotunda Battery and Starter Tester 010-00725 or equivalent tester is suggested.

When performing charging system tests, turn OFF all lamps and electrical components. Place transmission in NEUTRAL and apply parking brake.

CAUTION
- Do not make jumper wire connections except as directed. To do so may damage Generator (GEN).
- Do not allow any metal object to come in contact with the housing and internal diode cooling fins with key ON or OFF or short circuit will result and burn out diodes.

NOTE: Battery posts and cable clamps must be clean and tight to ensure accurate meter indications.

Load Test
1. Switch the Rotunda Battery and Starter Tester 010-00725 or equivalent to the ammeter function.
2. Connect the positive and negative leads of the Rotunda Battery and Starter Tester 010-00725 or equivalent to the battery.
3. Connect the current probe to the generator B+ output lead Circuit 30 (R).
4. With the engine running at 2000 rpm, adjust the Rotunda Battery and Starter Tester 010-00725 or equivalent load bank to determine the output of the generator. Refer to the Symptom Chart. Symptom Related Diagnostic Procedures

No-Load Test
1. Switch the Rotunda Battery and Starter Tester 010-00725 or equivalent to the voltmeter function.
2. Connect the voltmeter positive lead to the generator B+ terminal and the negative lead to ground.
3. Turn all electrical accessories off.
4. With the engine running at 2000 rpm, check the generator output voltage. The voltage should be between 13.0 and 15.0 volts. If not, refer to the symptom chart. Symptom Related Diagnostic Procedures