GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Oldsmobile 🢒 1998 🢒 LSS 🢒 Engine 🢒 Engine Electrical 🢒 Generator Noise Test

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

Perform an output test in order to help distinguish bearing noise from the magnetic noise, also called a whine. Refer to Generator Not Operating Properly . A shorted bridge diode will reduce output be 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) in order to determine if there is a bearing or magnetic noise.

In order to avoid damage to the electrical equipment, observe the following precautions:

    • Do not reverse the 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 the battery voltage directly to the regulator L terminal for testing. A 400 - 500 ohm resistor must be used.
    • Never disconnect the battery cables from the output terminal or the battery while the generator is operating.
    • When connecting a charger or booster battery to the car battery, refer to Battery Charging .

Trouble in the charging system can be detected by the following conditions:

    • The AMP indicator does not light with the ignition switch in the ON position before the engine start, or does not go out after the engine start. The driver information center displays Check Charging System.
    • Service Engine Soon light comes ON.
    • An undercharged battery as evidenced by slow cranking or a dark hydrometer. Refer to Battery Hydrometer Displays Dark or Yellow Dot .
    • An overcharged batter 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:

  1. Visually inspect the accessory drive belt for damage or looseness.
  2. Use the J 23600-B in order to check for proper belt tension.
  3. Inspect the charging circuit electrical connections for damage or looseness.
  4. Perform the Generator Electrical Test. Refer to Generator Not Operating Properly .