HEATER/A-C VACUUM RESERVOIR NOISE- NEW P/N

VEHICLES AFFECTED: 1986-87 'N' BODY

Cars built prior to February 1987 may exhibit a noise condition similar to a steering stop or bushing squawk. This nolse may be deceptive in that it can be quite laud and appear to be coming from the dash panel area of the car. The noise is actually the check valve and diaphragm inside the HVAC vacuum tank located on the right end of the HVAC case in the passenger compartment.

To diagnose the condition: With the engine running, operate the A/C control through its modes and listen for the noise. If the noise is present, then disconnect the vacuum source from the vacuum tank. The reservoir should hold vacuum for at least one mode change. If the reservoir leaks down or it is quiet when mode is changed, then replace the vacuum tank assembly.

The noise may be described as a whistle, a moan, a squawk, a hiss, a vacuum leak or a squeak. The correction is to replace the vacuum tank ,assembly with a service replacement part, 10000669, from GM PARTS.

The following are the VIN breakpoints:

Pontiac - HC814124 Buick - HM051662 Oldsmobile - HM256321

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.