Rear HVAC only blows hot air in '05 Tahoe

[Tahoe97]

Our '05 Tahoe, with nice cold air coming through the front vents, has only hot air blowing out of the rear vents when the rear HVAC is turned on. We have had the rear actuator 9.280 0 motor (part # 89018375) replaced by Chevrolet/GMC dealers 4 times in 5 years, most recently in April, 2023 (12k miles ago). I recently had to replace the blower motor resistor control module for the front HVAC unit as the front fan wouldn't run or ramp up. That front fan issue resolved with the new blower motor resistor control module. Is it possible that changing out this front blower motor resistor control module requires some reprograming of the rear HVAC actuator or is it likely that the rear HVAC actuator has failed again? Thank you forum members for your comments.

 

[Scottydoggs]

be best to just take the plastic panel off on the pass side rear and turn the controls to hot and cold and watch the actuator to see if its moving. you can take the actuator off and turn the knob by hand from hot to cold as well as a temp fix.

new actuators are like 15 bucks on rock auto. two screws hold it on and a plug. its in the great wide open too. the plastic panel other then maybe two screws at the very rear all just snap off/on.

 

[Tahoe97]

be best to just take the plastic panel off on the pass side rear and turn the controls to hot and cold and watch the actuator to see if its moving. you can take the actuator off and turn the knob by hand from hot to cold as well as a temp fix.

new actuators are like 15 bucks on rock auto. two screws hold it on and a plug. its in the great wide open too. the plastic panel other then maybe two screws at the very rear all just snap off/on.

I will follow your recommendation as step #1. Thanks

 

[Tahoe97]

Unfortunately the actuator knob/shaft into the air diverter box and its attachment to the upper door is broken. The actuator itself seems fine but it effectively has lost control of the upper and larger diverter door which it attaches to. So no matter what I do with the knob/ shaft, the door won't move and hold a position. Much bigger problem now with the entire system housing needing to be replaced.

 

[Scottydoggs]

Unfortunately the actuator knob/shaft into the air diverter box and its attachment to the upper door is broken. The actuator itself seems fine but it effectively has lost control of the upper and larger diverter door which it attaches to. So no matter what I do with the knob/ shaft, the door won't move and hold a position. Much bigger problem now with the entire system housing needing to be replaced.

lord thats a first. your gonna have to search for a exploded diagram of the rear HVAC box, to see how it comes apart and see what parts are broken and need to be replaced if possible. might be able to buy the whole box at a junk yard if need be. way cheaper then the dealership.

might be able to make head or tails of some of these. https://www.google.com/search?q=exp...iAYBkAYKkgcEMjMuMaAH-pAB&sclient=gws-wiz-serp

 

[Tahoe97]

This is what I need to replace

2000-2006 GM Auxiliary Air Conditioning Evaporator and Blower Upper Case 88891577 | OEM Parts Online

2000-2006 GM Auxiliary Air Conditioning Evaporator and Blower Upper Case 88891577

g.oempartsonline.com

 

[DRLexpress]

Going through the same thing as we speak.

I don't know why GM or an aftermarket company does not sell just the replacement door. I had the whole case (above link) in my cart and had to go to the next town for a doctors appointment. Town, 1.5 hrs away, also has my closest GM dealer. Checked with them and they were only a few dollars more than online by the time you figure shipping.
He is supposed to have it for me tomorrow. Let me know if you have questions about the job. Yes you can get the top case half off with out breaking AC/heat lines loose.

 

[Tahoe97]

Bingo. That is exactly the failure in my housing. Brilliant to make that door and shaft out of plastic knowing that it will cycle through high heat and cold for 20 years! A real rocket scientist designed that! Dumb ---.

 

[Tahoe97]

Going through the same thing as we speak.
View attachment 430972
I don't know why GM or an aftermarket company does not sell just the replacement door. I had the whole case (above link) in my cart and had to go to the next town for a doctors appointment. Town, 1.5 hrs away, also has my closest GM dealer. Checked with them and they were only a few dollars more than online by the time you figure shipping.
He is supposed to have it for me tomorrow. Let me know if you have questions about the job. Yes you can get the top case half off with out breaking AC/heat lines loose.

Let me know how your housing replacement goes. I may try it myself

 

[Fless]

It would be interesting to see if Q-Bond would repair something like this break.

 

[DRLexpress]

It would be interesting to see if Q-Bond would repair something like this break.

I thought about that but my luck it would fail tomorrow, and I would have to do it all over again.

 

[Fless]

I thought about that but my luck it would fail tomorrow, and I would have to do it all over again.

I think you could tell right away whether it would hold or not. I'd fix it and rough it up a little to see what it'll take. If it survives testing, I'd run with it. Besides, if you have to do it again it'll take half the time since you'll have the experience.

 

[oldchev]

I had this exact same problem on my 2004 Denali about 6 years ago.
I tried epoxy and clamps for 24 hours. Looked great and was strong. Put it in and broke 2 days later. Longer story but didn't hold.
I bought the new housing with door on ebay, then installed. No problem since.
I can say it is difficult getting into some areas for the clips that hold 2 halves together. I took pics and have instructions saved I can post later this week, if you still need it.
Doable. Take your time. I think the second time I took 4 hours or so.

 

[DRLexpress]

Let me know how your housing replacement goes. I may try it myself

Sorry it has been a couple days but finally got to it yesterday. Took about an hour or hour and a half. The only real problem I had was there are 2 studs in the lower case that go down through the floor in amongst the 4 heat and AC lines. You need to loosen the nuts on them (10mm deep socket) so you can wiggle things around enough to get the top case off. Just my luck both studs backed out of the case. That took an extra 15 minutes to figure out. Here are a couple pic's to show you what you are up against. Overall, pretty easy job. I had already bought 2 actuators when I thought that was the problem. Since they are easy to change, I reinstalled the old ones and they work fine. Guess I have 2 on the shelf for when they do die.