A/C Compressor - Moan/Vibration/Noise

GMC NUMBER:
91-1B-188

GROUP:
1B Air Conditioning

DATE:
June 1992

CORPORATE
NUMBER:
061201R



SUBJECT:
A/C COMPRESSOR MOAN/VIBRATION/NOISE (INSTALL SUCTION-DISCHARGE HOSE ASSEMBLY)

MODELS:
1988-91 C/K TRUCKS WITH AIR CONDITIONING (RPO C60)

THIS BULLETIN CANCELS AND REPLACES GMC TRUCK BULLETIN 90-1B-111, PUBLISHED IN NOVEMBER 1990. IT WAS REVISED TO INCLUDE THE 1991 MODEL YEAR AND ADD INFORMATION ON THE 1992 MODEL HOSES. ALL COPIES OF 90-1B-111 SHOULD BE DISCARDED.



Some 1988-91 C/K model trucks may develop a condition described as a moan, vibration, or noise when the A/C compressor is engaged. To address this condition, a suction discharge hose assembly has been released for service. This new hose assembly will be made of a different material, (nitrile), than the production assembly and dampens more vibration. 1992 models, although not equipped with nitrile hoses, are equipped with hoses made of a material with the same vibration transmission properties.

Important
The revised hose assembly alone will not solve all customer comments. It is essential that the revised service hose be used only after the following noise abatement procedures have been employed.

^ Check A/C system for grounding (hoses/pipes hitting hoses/pipes, body or engine).

^ Check mounting bolts for being loose, missing, or a blind hole.

^ Check drive belt for debris in the grooves or for wear.

^ Check that a brace kit has been installed from bulletin 88-T-56 (filed in group 1B) (Corporate Number 831203) or bulletin 91-1B-154 (Corporate Number 131208).

^ Check that the latest R4 compressor is being used. All 1990 and 1991 Model C/K trucks were built with the latest style A/C compressor.

When repairing 1988 and 1989 model C/K trucks, reference Truck Service Bulletin 89-1B-118 (Corporate Number 961205).

^ To determine whether the new nitrile hose assembly will lessen the A/C noise-moan-vibration, have a person in the cab listen to the noise at the engine speed where the noise is most prevalent. Have another person in front of the truck grab the suction hose with both hands. This will approximate the noise reduction which will result from replacement of the hose.





SERVICE PARTS INFORMATION
Nitrile Hose Assembly



WARRANTY INFORMATION
For vehicles repaired under warranty use:

Labor Operation: D3088

Labor Time: .4 hours

Add: .5 hours (discharge/charge A/C system)