A/C MOAN-VIBRATION NOISE, NEW SUCTION/DISCHARGE HOSE

Subject: AIR CONDITIONING MOAN-VIBRATION-NOISE

Model and Year: 1987-90 S/T TRUCKS WITH 2.8L ENGINE

TO: ALL CHEVROLET DEALERS

Some 1987-90 S/T model trucks may develop a condition described as a moan, vibration, or noise when the A/C compressor is engaged. To address this condition, Harrison Radiator has released a suction-discharge hose assembly for service. This new hose assembly will be made of a different material, nitrile, than the production assembly and dampens more vibration.

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 Dealer Service Bulletin No. 88-224-1 B.

* Check that the latest R4 compressor is being used. All 1990 model S/T trucks were built with the latest style A/C compressor. When repairing 1987 through 1989 model S/T trucks, reference Dealer Service Bulletin No. 89-280-1 B. Note that the latest style A/C compressor has an orange background label.

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

Part Number Application Quantity ----------- ------------------------------- -------- 15659196 1987-1990 S/T and LL2 (2.8L V6) 1

Parts are currently available through GMSPO.

WARRANTY INFORMATION

For vehicles repaired under warranty use:

Labor Operation Number: D3088

USE APPLICABLE LABOR TIME GUIDE FOR LABOR HOURS.

* When possible, use appropriate refrigerant recovery and recycling methods.

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.