Some 1990 "M" and "L" vans with 4.3L engines built prior to VIN LB133267 (Chevrolet) or LB509694 (GMC) may exhibit a noise/ vibration when the air conditioning compressor is engaged.
This noise/vibration is the result of a resonance set up in the serpentine accessory drive system with the air conditioning compressor engaged.
This condition may be corrected by installing a compressor brace kit, p/n #10118789, per the artwork and detailed instructions included in the kit.
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.