Hvac Fan Above My Head

98 Z71 SLT · October 5, 2008

Like title says, with the colder temps around here lately, the Auto HVAC temp sensor, located in the headliner, is buzzing like non-stop when my Tahoe is first started in AM.

As the little fan spends more time running, (anytime ignition is -on-) it starts to quiet down.

We all know, the purpose of this small fan is to send an accurate temperature signal to the HVAC module.

I pulled up a wiring schematic from Dealerworld, and it shows that the temp sensor and little fan are actually wired SEPERATE.

Have any of you just eliminated the "fan" portion of the sensor, with no ill-effects to the actual temp sensor itself?? While I order-up a new sensor, I'm looking to eliminate that BUZZING in the am's...

Zembonez · October 5, 2008

If you eliminate the fan, the sensor won't get any airflow and the climate control won't have a clue what to do. I wonder if you could locate that sensor and expose it to cabin air or place a fan somewhere else to blow air on it?

pm26 · October 5, 2008

I have a manual A/C in my truck, so no fan buzz, but there is some gurgling inside the dash once in a while. Is that still present in the 900 series?

Interestingly enough, I have several older Mercedes cars with auto climate control and the sensors do not have any fans. So no buzz.

BZZZZZZZZZZZZZZZZZZZZZZZZZZ

Zembonez · October 5, 2008

I have a manual A/C in my truck, so no fan buzz, but there is some gurgling inside the dash once in a while. Is that still present in the 900 series?

If you drain about half of the coolant out of the radiator into a clean drain pan and then pull the top hose off of the radiator and back fill through it until coolant starts coming out of the radiator, it will get the air bubble out of the heater core. I had that same problem on my 01 Silverado and it took me a month to figure out how to solve it.

Does that make any sense at all?

VMax2007 · October 5, 2008

I have a manual A/C in my truck, so no fan buzz, but there is some gurgling inside the dash once in a while. Is that still present in the 900 series?

If you drain about half of the coolant out of the radiator into a clean drain pan and then pull the top hose off of the radiator and back fill through it until coolant starts coming out of the radiator, it will get the air bubble out of the heater core. I had that same problem on my 01 Silverado and it took me a month to figure out how to solve it.

Does that make any sense at all?

Couldn't you just put a towel on your shoulder, throw the truck over your shoulder and pat it on the back a few times until it burps? Worked with my kids.

Zembonez · October 5, 2008

I have a manual A/C in my truck, so no fan buzz, but there is some gurgling inside the dash once in a while. Is that still present in the 900 series?

If you drain about half of the coolant out of the radiator into a clean drain pan and then pull the top hose off of the radiator and back fill through it until coolant starts coming out of the radiator, it will get the air bubble out of the heater core. I had that same problem on my 01 Silverado and it took me a month to figure out how to solve it.

Does that make any sense at all?

Couldn't you just put a towel on your shoulder, throw the truck over your shoulder and pat it on the back a few times until it burps? Worked with my kids.

It's worth a shot.

satori · October 5, 2008

I think I saw a thread on here in the last week where there's a TSB on that fan noise.

Wingnut · October 5, 2008

I have a manual A/C in my truck, so no fan buzz, but there is some gurgling inside the dash once in a while. Is that still present in the 900 series?

If you drain about half of the coolant out of the radiator into a clean drain pan and then pull the top hose off of the radiator and back fill through it until coolant starts coming out of the radiator, it will get the air bubble out of the heater core. I had that same problem on my 01 Silverado and it took me a month to figure out how to solve it.

Does that make any sense at all?

Started doing it again about a week ago.

Zembonez · October 5, 2008

I have a manual A/C in my truck, so no fan buzz, but there is some gurgling inside the dash once in a while. Is that still present in the 900 series?

If you drain about half of the coolant out of the radiator into a clean drain pan and then pull the top hose off of the radiator and back fill through it until coolant starts coming out of the radiator, it will get the air bubble out of the heater core. I had that same problem on my 01 Silverado and it took me a month to figure out how to solve it.

Does that make any sense at all?

Started doing it again about a week ago.

That's funny. I had it happen twice while I owned it. Never lost any coolant though... WTF?

How is Fred these days?

Wingnut · October 5, 2008

That's funny. I had it happen twice while I owned it. Never lost any coolant though... WTF?

How is Fred these days?

I had to add coolant a couple of months ago. About 1/3 gallon or so. Not sure where it went??? I think that bloody Sasquatch took it. It's not leaking and the oil looks fine.

Fred is doing great. I scored a used head unit off of a guy on LS1GTO.com that'll play MP3's off of a USB cord plugged into the back of it and THEN hit a double score when Radio Shack had an open-box 32gb USB memory stick for $18. So I put that in about a week ago and it's freakin AMAZING for functionality. I've got 13 gig of music (got tired of moving files and stopped there) with voice prompts and a remote control. It's flippin' sweet.

Zembonez · October 5, 2008

I had to add coolant a couple of months ago. About 1/3 gallon or so. Not sure where it went??? I think that bloody Sasquatch took it. It's not leaking and the oil looks fine.

Fred is doing great. I scored a used head unit off of a guy on LS1GTO.com that'll play MP3's off of a USB cord plugged into the back of it and THEN hit a double score when Radio Shack had an open-box 32gb USB memory stick for $18. So I put that in about a week ago and it's freakin AMAZING for functionality. I've got 13 gig of music (got tired of moving files and stopped there) with voice prompts and a remote control. It's flippin' sweet.

That's cool. What are the miles up to?

This thread will return to its regularly scheduled programming shortly.

Wingnut · October 5, 2008

I'm not sure...'bout 120 or so. I don't check it very often, he's just clicking along, waiting for me to get the last few dents removed and put a new windshield in.

/sorry about the threadjack Super Stealth

Zembonez · October 5, 2008

It sounds like those overhead sensor fans are yet another good reason NOT to get automatic climate control. How hard is it to reach over and adjust the HVAC controls? Some of the optional equipment that we pay extra for amazes me.

They usually just make a simple and effective system more likely to have issues.

pm26 · October 5, 2008

I have a manual A/C in my truck, so no fan buzz, but there is some gurgling inside the dash once in a while. Is that still present in the 900 series?

If you drain about half of the coolant out of the radiator into a clean drain pan and then pull the top hose off of the radiator and back fill through it until coolant starts coming out of the radiator, it will get the air bubble out of the heater core. I had that same problem on my 01 Silverado and it took me a month to figure out how to solve it.

Does that make any sense at all?

I read several threads on this issue and the consensus was that this was caused by the A/C system, not cooling system. Maybe we are not talking about the same think. Gurgling I am talking about only occurs with the A/C running.