Generator On-Vehicle Tests

Troubleshooting or diagnosis is required before the actual service can be made to 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: Information contained in the Rotunda Alternator, Battery and Starter Tester Procedure Manual will give complete directions on checking out the charging system.

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

CAUTION:
^ Do not make jumper wire connections except as directed. To do so may damage the generator.
^ Do not allow any metal object to come in contact with the housing and the internal diode cooling fins with key on or off. A short circuit will result and burn out the diodes.

Battery posts and cable clamps must be clean and tight for accurate meter indications.

Load Test
1. Switch the Rotunda Alternator, Battery and Starter Tester to the ammeter function.
2. Connect the positive and negative leads of the Rotunda Alternator, Battery and Starter Tester to the battery.
3. Connect the current probe to the generator B+ output lead, Circuit 38 (BK/O).
4. With the engine running at 2000 rpm, adjust the Rotunda Alternator, Battery and Starter Tester load bank to determine the output of the generator.

No-Load Test
1. Switch the Rotunda Alternator, Battery and Starter Tester 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, Symptom Related Diagnostic Procedures