Speaker like object in headliner

Does anyone know what that round speaker like object is located in the headliner just above the driverside door? It usually makes a buzzing sound at start up, but then quiets after a while. I have no clue. Any ideas?

What find of car is this from?????????

What find of car is this from?????????

98 blazer LT 4x4

Do black helicopters circle your house in stealth mode all night too? :D

It's the Db noise sensor for the Radio SVC (Speed Volume Control). You should have a seeting on your radio that enables that sensor to read the cabin noise level and increase/decrease the radio level accordingly. If it's functioning you should notice that the radio/CD volume increases slighlty as you accelerate to highway speeds and decreases as you slow down.

It's the Db noise sensor for the Radio SVC (Speed Volume Control). You should have a seeting on your radio that enables that sensor to read the cabin noise level and increase/decrease the radio level accordingly. If it's functioning you should notice that the radio/CD volume increases slighlty as you accelerate to highway speeds and decreases as you slow down.

Never saw those in the blazer before... What he is describing is more likely the cabin air filter...

I think this is what he's talking about...

http://img476.imageshack.us/img476/2141/misc01323mo.th.jpg (http://img476.imageshack.us/my.php?image=misc01323mo.jpg)

As far as I know I don't have a cabin filter in my truck so it could be for the radio. I always wondered too.

yep i got one also 99 LT, i was wondering what the hell that was thanks

Does anyone know what that round speaker like object is located in the headliner just above the driverside door? It usually makes a buzzing sound at start up, but then quiets after a while. I have no clue. Any ideas?


UPDATE! I was told by a service writer it has something to do with the electronic climate control. Does anyone NOT have this type of system but DO have this sensor in their headliner? I'm just trying to validate the dealer's statement.

I think this is what he's talking about...

http://img476.imageshack.us/img476/2141/misc01323mo.th.jpg (http://img476.imageshack.us/my.php?image=misc01323mo.jpg)

As far as I know I don't have a cabin filter in my truck so it could be for the radio. I always wondered too.

That's exactly what I'm speaking of...

That's exactly what I'm speaking of...


Make sense to me, but I was told by the dealership a few years back it was a sensor for the automatic sound control. Automatic radio volume adjustment was an option on my 98 Blazer LT. Who knows maybe the mechanic was guessing.

What's funny is Chevy told me they didn't know what it was....customer service that is.

I haven't seen one before....... possibly for hands free phone use? on star?

I don't believe Onstar was around in 98 - I could be wrong though. I can't believe everyone is stumped!

rasmith527 - do you have automatic heat controls?

On star was started in 98 for some models, Blazers didn't officially get it until 99, but I thought it may be possible that some got it early...... like OBD II was intended for 96+, however, some 95s have OBD II.

I'm not saying that it is On-Star, it was just a guess.

You are breathing in poison gas.........

I have a full set of service manuals I will look...never had one on my 99....I'd pull a section of the head liner just to see what the hell it is....maybe it's a small camera/speaker installation so that your wife can keep track of you ......

I will let you know if I find out anything.... :rofl: