Loud Buzz Type Noise Heard Inside Vehicle (Inspect Automatic Level Control Air Compressor Bracket)

Some customers may comment on a loud buzz type noise that can be heard inside the vehicle. This noise may be duplicated by turning on the air compressor at the auxiliary air outlet located in the rear cargo area of the vehicle.

The cause of this noise may be from the automatic level control air compressor grounding out on its mounting bracket. This occurs when ice builds up or small rocks become wedged between the compressor head and the forward end of the compressor bracket. Also, the forward lower part of the bracket may become bent up and rearward and touch the compressor.

The noise is loudest inside the vehicle due to the vibration transmitted from the compressor directly to the vehicle body when the rubber isolators are bypassed by the grounding condition.

1. Confirm that the noise can be heard inside the vehicle with the compressor running. Close all doors and windows and start the vehicle. Normally about 30 seconds later, the compressor will cycle for about 5 seconds. If not, turn the compressor on at the rear auxiliary air outlet.



2. Inspect the area (1) between the compressor head and the forward end of the compressor bracket for ice build up or rocks. Remove any material or debris.
3. Inspect the lower part (2) of the assembly bracket and make sure it is not touching the compressor. If it is, bend it back to its original position.



4. If the vehicle was built before April 2003, it will not have a rubber shield on the forward area of the assembly bracket. In this case, install shield kit, P/N 88957138 by drilling two 12mm holes (1) as shown. Drill the first hole and then use the shield as a template to locate the second hole. Use the two fasteners provided to secure the shield to the compressor assembly bracket.
5. Confirm that the noise has been eliminated.

Parts are currently available from GMSPO.

For vehicles repaired under warranty, use:

*This is a unique labor operation number for use only with this bulletin. This number will not be published in the Labor Time Guide.