Humming noise in headliner above driver

[FijiRob]

I have noticed a humming sound coming from the round cap that is located on the headliner directly above the driver (I have a 2002 Yukon). The cap has small holes and appears to be a microphone for the OnStar system, but I am unsure. Before I pull off the cap and take it apart, I wanted to know what's behind the cap. The humming sound only happens when it is cold outside. Once the car warms up, the humming goes away. Any help would be appreciated.

Thanks,

Rob

 

[Modded]

Its a temp. aspirator, its prob. gone bad hence the buzzing noise it makes.
Real cheap to fix at the dealer.

 

[Anthony]

Or a simple solution to try first is go to any store that sells "Canned air" like here:http://www.bestbuy.com/site/Dynex%26%23174%3B+-+Compressed+Gas+Duster/9464581.p?id=1218109500816&skuId=9464581&st=canned%20air&cp=1&lp=4


And spray some air up there a few times and see if the noise stops. Sometimes all that happens is the fan on the temp. aspirator is "dirty" aka covered with dust and just needs a good air spray to get it to be quiet.

 

[jdpromo33]

It could also be a vibration noise from something in the headliner. By the drivers door you can pull down the liner and put your hand in there to see if something is loose and rattling or humming.

When you get the noise try pressing up on the headliner and see if the noise stops first.

Just my 2 cents

 

[sully]

my 03 does the same thing from that round piece right above my head and from the other one in the back above the rear seats. It sounds like it is winding up and down when I start/stop the engine. It is getting worse so any input on what this is and how to fix it would be great. I thought those were little speakers or microphones for the onstar but I will try the canned air thing tomorrow and see how that goes. If they are air sensors that have a fan inside that makes more sense cause it sounds like a fan slowing down when I kill the engine.


UPDATE: Well I don't know if this is the right piece but I got it on Ebay for $31 shipped, will update again after I get it installed if it fixes the problem. Click to see part