ALTERNATOR WHINE-LEFT CHANNEL MODIFY GROUND TO RADIO

MODELS: 1985 and 1986 S, T, AND M MODEL TRUCKS EQUIPPED WITH AN ETR AM/FM STEREO CASSETTE WITH OR WITHOUT GRAPHIC EQUALIZER (2000 SERIES RADIO WITH VACUUM FLORESCENT DISPLAY)

THIS BULLETIN CANCELS AND SUPERSEDES 86-B-36 (JANUARY,1986), ALL COPIES OF WHICH SHOULD BE DESTROYED.

The ground wire used in the instrument panel harness may cause a ground loop that could result in alternator whine heard in the left channel of the radio.

If alternator whine is heard, remove the ground lead (black wire) from the black 4-pin connector in the back of the radio. If the removal of the ground lead causes the altenator whine to disappear, correct the whine condition by doing the following:

1. Cut the black ground lead in the black connector.

2. Attach one end of a 16 guage wire to the chassis of the radio and the other end to a good ground close to the radio. When attaching the wire to the radio chassis, use one of the chassis case screws or a mounting lug.

3. Reconnect the radio.

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.