Component Tests and General Diagnostics

Noise from a Generator may be caused by a loose drive pulley, loose mounting bolts, worn or dirty bearings, defective diode, or- defective stator. A high frequency whine or magnetic noise may be heard at full output and is normal.

An output test as described in the "GENERATOR FUNCTIONAL CHECK" should be performed to help distinguish bearing noise from magnetic noise (also called whine). A shorted bridge diode will reduce output by 1/3 of the rating and have a "growling" noise when at high load. It is also helpful to listen to the generator with a moderate load (engine cooling fans or headlights ON) to determine if there is a bearing or magnetic noise.

To avoid damage to the electrical equipment, always observe the following precautions:
^ Do not reverse connections to the Generator.
^ Do not short across or ground any of the terminals in the charging circuit except as directed by the service manual.
^ Do not apply battery voltage directly to the regulator "L" terminal for testing. A 400-500 ohm resistor must be used.
^ NEVER disconnect battery cables from the output terminal or battery while the Generator is operating.
^ When connecting a charger or booster battery to the car battery, refer to Battery. Battery

Trouble in the Charging System will show-up as one or more of the following conditions:
^ BATTERY NO CHARGE", "BATTERY VOLTS LOW" or "BATTERY VOLTS HIGH" messages.
^ "SERVICE ENGINE SOON."
^ Battery Telltale (Export Only).
^ An undercharged battery as evidenced by slow cranking or dark hydrometer, refer to Battery. Battery
^ An overcharged battery as evidenced by spewing of electrolyte from the vents.

If an undercharged or overcharged battery condition occurs, the following procedure may be used to diagnose the charging system. Remember that an undercharged battery is often caused by accessories being left on overnight or by a faulty switch which allows a lamp (such as a trunk or glove box lamp) to stay "ON". Refer to PARASITIC LOAD TEST in Battery.
1. VISUAL CHECKS: All Generator diagnosis should begin with a visual inspection. Visual inspection should include checking the serpentine belt for damage or looseness. Check for proper belt tension with belt tension gage. Inspect all charging circuit electrical connections for damage or looseness.
2. CHECK FOR IPC AND PCM CODES: After performing the Generator visual inspection, check for IPC trouble codes following the procedure.
3. PERFORM GENERATOR FUNCTIONAL CHECK: Perform the "GENERATOR FUNCTIONAL CHECK" trouble tree. This Generator does not have a test hole.
4. PERFORM MESSAGE DIAGNOSIS: If the problem is related to a "BATTERY NO CHARGE", "BATTERY VOLTS LOW", "BATTERY VOLTS HIGH" messages or -"SERVICE ENGINE SOON" message.