Document ID# 1639237
Subject: Buzz Noise From Headliner Above Driver - keywords ac air aspirator cover fan grille HVAC interior microphone sensor speaker temperature vent vibration #PIT3511 - (03/29/2005)
Models: 2000-05 Cadillac Escalade
2002-05 Chevrolet Avalanche
2000-05 Chevrolet Silverado, Suburban, Tahoe
2000-05 GMC Sierra, Yukon, Yukon XL, Yukon Denali
The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in the PI.
Condition/Concern:
Dealer or customer may comment that they have a buzz or vibration noise emanating from the headliner in an area that looks like microphone or a speaker.
Recommendation/Instructions:
The plastic escutcheon grill, which is round and about the size of a half dollar and located just above the driver to the left, is the interior ambient temperature sensor. The sensor is used in conjunction with the automatic HVAC (C68). On occasions, this sensor has been known to make a buzz or rattle sound. The sensor uses a small fan to pull air over the sensor. This buzz noise may be intermittent.
Although it may not be possible to alleviate all of the buzz or noise from this sensor, Engineering has found that if the sensor is installed incorrectly that it may bind and cause the fan to make a buzz noise. Remove the sensor and while doing so check for any binding. Reinstall the sensor and re-test. If the noise is still present, the sensor itself may be noisy and require replacement.
Thats how I know it was a microphone for our OnStar
