The generator light may f licker when the pulse wipers are used, on the 1988 P car.
The flicker is caused by voltage spikes from the wiper motor. The generator sees the voltage spikes as high voltage signals, and turns the generator off for a very short time, causing the light to flicker, or the gauge to drop. This condition causes no harm to the generator or the electrical system.
This condition may be corrected by installing a diode in the brown wire at the generator connector. The diode is part number #lN4003, available from electronic supply stores, or may be obtained from GM Parts as part number #12085207.
1. Disconnect negative battery cable.
2. Remove the connector from the generator.
3. Remove the brown wire from the conduit. Cut out enough of the brown wire to install the diode. Make sure the diode is installed with the arrow toward the generator. Solder the diode in place, then tape the diode and wire, and return to the conduit.
4. Attach the connector to the generator.
5. Reconnect negative battery cable.
6. Start the vehicle, and insure that the generator is charging properly, and the light is working correctly.
General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.