HVAC issue: no heat unless set at 90 degrees 07-14 Tahoe

[jared999]

I have a 2009 Tahoe LTZ. I have no heat unless I set it to 90 on the HVAC control unit. I've narrowed it to a bad cabin Air Temperature Sensor. Some people refer to it as the aspirator but on gm sites, its called a cabin Air Temperature Sensor.

Anyone know the precise location of this sensor? Headliner driver side? instrument cluster area?


In older tahoe model years, there is a plastic circular grill located on the headliner, driver side that makes the sensor easy to find and its referred to as an aspirator. Threads and videos on those older model year issues (99-06) are fairly easy to find. Not for the 07-14 Tahoes, I see ZERO videos on youtube related to this issue. I should add, no such plastic vent exists on my headliner.

I want to mention - rock auto shows two types. The boxy style and a pin / push pin style. Their push pin version has a detail of "Instrument Panel Air Duct Temperature Sensor; " So naturally, that makes me think its near the instrument panel.

TIA

 

[gooffeyguy]

I think @Doubeleive had this issue and had to replace the cabin air temp sensor. I tagged him so maybe he'll get in here and bless us with his knowledge

 

[swathdiver]

I have a 2009 Tahoe LTZ. I have no heat unless I set it to 90 on the HVAC control unit. I've narrowed it to a bad cabin Air Temperature Sensor. Some people refer to it as the aspirator but on gm sites, its called a cabin Air Temperature Sensor.

Anyone know the precise location? The driver side? Passenger side? Near the visors, or further back?


In older tahoe model years, there is a plastic circular grill located on the headliner, driver side that makes the sensor easy to find and its referred to as an aspirator. Threads and videos on those older model year issues are fairly easy to find. Not for the 07-14 Tahoes. no such plastic trim exists on the headliner.

I want to mention - rock auto shows two types. The boxy style and a pin / push pin style. Their push pin version has a detail of "Instrument Panel Air Duct Temperature Sensor; " So naturally, that makes me think its near the instrument panel.

TIA

Well, an LTZ Tahoe ought to have 1 or 2 of those little vents right above the driver's head and to the side of the moonroof. 2 if the engine is an L9H.

 

[Doubeleive]

I have a 2009 Tahoe LTZ. I have no heat unless I set it to 90 on the HVAC control unit. I've narrowed it to a bad cabin Air Temperature Sensor. Some people refer to it as the aspirator but on gm sites, its called a cabin Air Temperature Sensor.

Anyone know the precise location? The driver side? Passenger side? Near the visors, or further back?


In older tahoe model years, there is a plastic circular grill located on the headliner, driver side that makes the sensor easy to find and its referred to as an aspirator. Threads and videos on those older model year issues are fairly easy to find. Not for the 07-14 Tahoes. no such plastic trim exists on the headliner.

I want to mention - rock auto shows two types. The boxy style and a pin / push pin style. Their push pin version has a detail of "Instrument Panel Air Duct Temperature Sensor; " So naturally, that makes me think its near the instrument panel.

TIA

first question is did this problem just happen all on it's own or did you change the main hvac control panel out?
the reason I ask is because that is exactly what I did because the buttons were worn off and a new oem control was not that much, however unbeknownst to me the replacement control needed to be programmed to my truck and it was looking for a non-existent temperature sensor and it would only produce heat if turned up to 90deg, set it to 89 and it would go right back to cold. As James stated there are 2 sensors in the headliner one is right above the drivers seat possibly along with a bose mic that looks just like it if you have the bose system, the 2nd one is above the passenger side 2nd row seat in the headliner. they are the same part used in the 2003-2014 and cost about $25 so if one of those is your issue it is easy to find and easy to replace, mine was looking for a 3rd one that would supposedly be in the headliner in the rear cargo area drivers side but those do not exist in our trucks (that was my issue and the calibration file for the hvac control for my vin corrected the problem). The small temperature sensor you refer to are inside the hvac tube and there is around 6 or so of them throughout the vehicle, should you locate one they can be tested with a meter and a blow dryer, attach the meter to the two legs of the sensor and set it to ohms, as you blow hot air on it the ohm's should change. also the harness connector that said sensor plugs into should read 5v. those little sensors seem to be pretty hardy and I have never head of one failing, the ones in the headliners do go funky and could cause your issue if it is not the main control or a actuator.

 

[jared999]

Well, an LTZ Tahoe ought to have 1 or 2 of those little vents right above the driver's head and to the side of the moonroof. 2 if the engine is an L9H.

View attachment 368009

I definitely have an LTZ and I don't have that vent. Perhaps the headliner was redone and they covered it. Also makes me wonder if mine is near the instrument cluster.
Thank you for the photo - I will double check that area. Even with no vent, maybe there is one up there.

 

[jared999]

first question is did this problem just happen all on it's own or did you change the main hvac control panel out?

Yes I did swap my hvac control out.


How did you program the replacement? Can it be done 'at home'?

 

[Doubeleive]

Yes I did swap my hvac control out.


How did you program the replacement? Can it be done 'at home'?

you need a tech2 and pay for the service contract online, they have made some changes but generally it used to be $40 for 2 years "per vin"
if you plan on doing more and more maintenance yourself a clone tech2 runs about $300 and will pay it's self in no time.
otherwise you can just take it to the dealer and ask them to install the calibration file for your vin and that should resolve it. generally that service runs about $120 but can vary from dealer to dealer, you can go to any GM dealer for that, buick, gmc, chevy, cadillac, etc

 

[swathdiver]

I definitely have an LTZ and I don't have that vent. This makes me wonder if mine is near the instrument cluster.
Thank you for the photo - I will double check that area. Even with no vent, maybe there is one up there.

How long have you had the truck and was the headliner ever replaced? I've never seen without at least one but admittedly doubt I've seen them all!

 

[jared999]

you need a tech2 and pay for the service contract online, they have made some changes but generally it used to be $40 for 2 years "per vin"
if you plan on doing more and more maintenance yourself a clone tech2 runs about $300 and will pay it's self in no time.
otherwise you can just take it to the dealer and ask them to install the calibration file for your vin and that should resolve it. generally that service runs about $120 but can vary from dealer to dealer, you can go to any GM dealer for that, buick, gmc, chevy, cadillac, etc

Thank you.

I also need to recalibrate or reprogram my actuator(s). The guides for "at home" programming don't work for me. Seems like most of them are geared to 99-06 Tahoes and so forth.

Maybe I will pick up a clone tech 2 so that I can get all of that sorted. I'll have to do some research to make sure what I buy can perform what I need.

 

[Doubeleive]

Thank you.

I also need to recalibrate or reprogram my actuator(s). The guides for "at home" programming don't work for me. Seems like most of them are geared to 99-06 Tahoes and so forth.

Maybe I will pick up a clone tech 2 so that I can get all of that sorted. I'll have to do some research to make sure what I buy can perform what I need.

pulling the hvac fuse or disconnection the battery for a couple minutes makes them self-calibrate, you can hear them doing it if you just turn the key on afterwards

 

[jared999]

pulling the hvac fuse or disconnection the battery for a couple minutes makes them self-calibrate, you can hear them doing it if you just turn the key on afterwards

I didn't see instructions for the 07-14 model year specifically, but tried to self calibrate several times based on 99-06 tahoe/sierra/suburban instructions and youtube video(s) that I found. I figured they would be the same.
Nothing worked.
1. set AC to auto.
2. disconnect battery for 2, 5, 10 and 60 minutes. (each one was a different attempt).
3. reconnect battery
4. turn ignition switch to on, but not starting the car. The AC defaults to 74 degrees.
5. wait for acuators to self calibrate.

Nothing happened.
I should mention - I replaced the mode actuator recently, which is why I need to recalibrate.

 

[Doubeleive]

I didn't see instructions for the 07-14 model year specifically, but tried to self calibrate several times based on 99-06 tahoe/sierra/suburban instructions and youtube video(s) that I found. I figured they would be the same.
Nothing worked.
1. set AC to auto.
2. disconnect battery for 2, 5, 10 and 60 minutes. (each one was a different attempt).
3. reconnect battery
4. turn ignition switch to on, but not starting the car. The AC defaults to 74 degrees.
5. wait for acuators to self calibrate.

Nothing happened.
I should mention - I replaced the mode actuator recently, which is why I need to recalibrate.

disconnecting the battery will make them self calibrate, doesn't matter what the control was set at. when you see the control go back to 74/74 then you know it has reset,
you can confirm by watching the center metal notch & marks in any of the actuators, you will see it move all the way forward and reverse and return to center.
you can also hear them moving they are rather quiet but if you listen carefully you can hear them, become one with the machine lol.

 

[jared999]

disconnecting the battery will make them self calibrate, doesn't matter what the control was set at.

Got it.

you can confirm by watching the center metal notch & marks in any of the actuators, you will see it move all the way forward and reverse and return to center.
you can also hear them moving they are rather quiet but if you listen carefully you can hear them, become one with the machine lol.

Well, I've never looked at any of the actuators when doing this. I suppose I can eyeball the one under / to the left of the glovebox. That's the easiest one to get to.
Based on results, though, the calibration hasn't worked for me. I'm only getting air from the front vents. not the top, not the bottom. The mode actuator was replaced with a new OEM GM actuator, btw.

Also, thank you for taking the time to respond to me in this thread I appreciate it.

 

[swathdiver]

They do self-calibrate with every ignition cycle, sort of. I've never been successful without using the Tech-2.

 

[jared999]

How long have you had the truck and was the headliner ever replaced? I've never seen without at least one but admittedly doubt I've seen them all!

I've had it for a few years. It's possible the headliner was redone, before I purchased it.

 

[jared999]

So at this point I will either locate a clone that can program things (not just spit codes) or find a shop with a tech 2. I'm in NW Houston so I'm sure it won't be hard to find a place.
My local chevy dealer is out of the question, unfortunately. They wanted an hour labor to program my new fob, which took me all of 2-3 minutes to do. That time spent includes walking to my tahoe and walking back into my house

I will report back once I have results. It may be a few weeks before I can buy one of those things.

 

[Doubeleive]

so you replaced the mode actuator? looked like this?

 

[jared999]

so you replaced the mode actuator? looked like this?
View attachment 368167

Yep, I replaced that with an OEM GM part when I pulled the dash out, even though nothing was wrong with the original as the modes worked fine. Mostly it was the thinking of "the dash is out replace everything".

 

[Doubeleive]

Yep, I replaced that with an OEM GM part when I pulled the dash out, even though nothing was wrong with the original as the modes worked fine. Mostly it was the thinking of "the dash is out replace everything".

if you still have old one you might try putting it back in and see what it does, if it works then that one may be no good. just speculation it shouldn't take a tech2 to make it work

 

[jared999]

if you still have old one you might try putting it back in and see what it does, if it works then that one may be no good. just speculation it shouldn't take a tech2 to make it work

I suppose new oem parts can be faulty, and I do have the old one. Based on what others have said here and else where, I'll try a tech 2 first before I pull the dash out again.