A/C NOISE/VIBRATION INSTALL BRACE KIT

SUBJECT: AIR CONDITIONER NOISE/VIBRATION (INSTALL BRACE KIT/POSSIBLE INERTIA RING PULLEY)

VEHICLES AFFECTED: 1988-1991 C/K, R/V TRUCKS WITH A/C AND 7.4L ENGINE

Condition:

-------------- Some C/K and R/V trucks with 7.4L engine may exhibit a noise/vibration when the air conditioning is engaged.

Cause:

------ This noise/vibration is the result of a resonance set up in the serpentine accessory drive system with air conditioning on.

Correction:

----------- This condition may be improved by installing a brace kit. The installation instruction included in the brace kit must be followed carefully. On some trucks, the addition of an inertia ring pulley may be required. on C/K models refer to Product Service Bulletin #91-1-108 for new Suction Discharge Hose Assembly.

Model Year Part Number Description --------- ------------ --------------------------------- 1988-91 6553148 Pulley and Bearing Assembly A/C Comp. 1988-90 10187643 Brace Kit - A/C Vibration and Noise 1991 10187645 Brace Kit - A/C Vibration and Noise

Use the most applicable Labour Operation and Time from the Canadian Labour Time Guide.

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.