GM Service Manual Online
For 1990-2009 cars only

Verify the following conditions before performing the diagnostic procedures on the vehicle:

    • The system wiring is in the proper condition.
    • The generator belt is not slipping.
    • The battery must be fully charged for a valid test of the charging system. Refer to Battery Is Undercharged or Overcharged

Notice: To avoid damaging the vehicle's electrical system, observe the following precautions:

   • Do not polarize the generator.
   • Do not short across or ground any of the terminals in the charging circuit, except as specifically instructed herein.
   • NEVER operate the generator with the output terminal open-circuited.
   • Make sure the generator and battery have the same ground polarity.
   • When a connecting charger or booster battery to the vehicle's battery, connect the negative to negative and the positive to positive.

Faulty operation of the charging system will appear as one or more of the following conditions:

    • Unusual operation of the charging indicator lamp on vehicles without gauges
    • An undercharged battery
        Slow cranking or a dark battery hydrometer indicates an undercharged battery. Refer to Battery Charging .
    • An overcharged battery
        Excessive gassing of electrolyted from the battery vents indicates an overcharged battery. Refer to Battery Charging .