1984-87 GRAND PRIX SERIES
An A/C compressor moan or vibration at idle or off idle can be caused by a drive belt without proper tension. We continuously receive reports that technicians fail to achieve proper belt tension because they guess at the tension rather than use a belt tension gage. The belt tension specifications are listed in Section 6B of the service manual, and it is essential that the belt tension gage be used.
Another cause of moan or vibration that should not be overlooked is compressor mounting bracket bolts. Make sure that the bolts are all tight.
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.