Hum from OnStar Speakers?

[robrr44]

Hey everyone, I was hoping someone might be able to guide me in the right direction with an annoying hum coming from what I believe are the OnStar speakers. There are two small (about 1") speakers, one in the ceiling above the driver, and one in the rear on the drivers side. They have an annoying hum coming from them when I start the vehicle. Its not really audible when driving with the radio on but are quite loud when just idling and the radio isn't playing. Any suggestions as to how to locate the culprit to this problem? Thanks!

 

[Bedhead514]

I don't think either are OnStar speakers. The one above the driver's seat is a temp sensor connected to the cabin heating and cooling system, and I imagine the one in the rear is the same thing. There's a little fan that pulls air to the sensor, and that's the noise culprit. You can try and clean the fan to stop the rattle, or replace it.

 

[robrr44]

Thanks Bedhead! I assume I just need to remove the headliner to reach the fans?

 

[TheYuk]

Before you remove the headliner get a can of dust off and spray them real good with them running then with them off. I did this and it fixed the annoying sound. They get dust build up in them, even worse if you smoke.

 

[cheerless]

thanks

I have this annoying hum also...time to head to Staples and get a can of air.

 

[NathanJax]

Called an aspirator fan...



Here is the GM bulletin regarding it...

Originally Posted by GM

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.