A/C - Whistling Noise With Blower Fan Turned ON

Number:
92-266-1A

Section:
1A

Date:
AUGUST 1992

Corporate Bulletin No.:
261205

ASE No.:
A7



Subject:
WHISTLING NOISE WITH BLOWER FAN TURNED ON


Model and Year:
1992 C/K TRUCKS



Some 1992 C/K trucks may make a whistling type noise with the blower fan turned on. Noise may occur in all modes or in only one mode often at higher blower speeds. The cause of the noise is usually an air gap or hole between the module seams.

The noise has often been mistakenly diagnosed as blower motor noise, especially if the gap is located between the scroll cage and the evaporator case. The noise source can often be verified by applying pressure to various places on the module and scroll case and noting a change in the noise. Running a hand along the seams can also produce a variation in module noise. True blower motor noise should remain the same when either of these techniques are used.

Areas of the module that contain unheated air are already sealed but may still cause a noise if the sealer does not fully cover the gap.





Most leaks can be found around the tongue and groove joint and can be repaired by separating the module seam, cleaning if necessary, and applying black RTV sealer P/N 12345739 (6/3.35 oz.tubes) then reassembling (Figure 1).

PARTS INFORMATION

Part Number Description Quantity

12345739 Black RTV Sealer Part number is for
six 3.35 oz. tubes

Parts are currently available at GMSPO.

WARRANTY INFORMATION

For vehicles repaired under warranty use:

Labor Operation:
D1410

Use applicable labor time guide for labor hours.