A/C NOISE/INSUFF./INOP COOLING REPLACE PRESS. CYCLING SWITCH

SUBJECT: A/C NOISE/INSUFFICIENT COOLING/INOPERATIVE (REPLACE PRESSURE CYCLING SWITCH) (Revised to correct 1st Paragraph)

VEHICLES AFFECTED: 1988-89 C/K TRUCKS

Some 1988-89 C/K trucks may experience an A/C pressure cycling switch failure. With the start of Production 1989, a new pressure cycling switch (part number 3096605) was used on the C/K trucks. This switch was also released on bulletin 88-1-157 as a fix for a noisy cycling switch. Sometimes, the pressure cycling switch has difficulty cycling the compressor clutch at the low set point. When this happens, the compressor clutch will rapid cycle or "flutter". This cycling will be so fast that the clutch will not completely disengage. Customer comments could be for the noise associated with the rapid clutch cycling, insufficient cooling due to clutch slippage, or inoperative compressor.

Effective Julian date 9020 (1989, Jan 20), the switch design was revised (same part number 3096605) to correct this problem. If a customer reports A/C noise, insufficient cooling or compressor failure; the pressure cycling switch should be checked for the correct Julian date -- 9020 or greater. The Julian date can be found on the bottom part of the switch (figure 1). If incorrect, the switch should be replaced with one that has a Julian date of 9020 or greater.

IMPORTANT: DO NOT CHANGE COMPRESSOR, even though the clutch driver may be discoloured, unless the compressor is seized.

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.