[black07sierra]

Truck is new body style 07. Has the auto climate control. Every now and then ab quits blowing from main vents and goes to defrost. Only way to make it go back to main vents is to shut truck off and I guess it resets itself. But in a day or two it will do it again. Anyone else having these issues or know what it is?

 

[GM Customer Service]

Have you brought this to the attention of your local dealer? I can also look into this for you with your VIN. Please feel free to keep me posted via private message either way. Thank you.

Tricia, GM Customer Service.

 

[black07sierra]

Truck is out of warranty. Powertrain only. I'll be happy if my dealer ever comes up with a way to fix the oil burning issue. They've done everything other than replace the engine and it still burns oil. They just top it off now. :/

I was hoping someone else had this issue so I knew where to start fixing.

 

[black07sierra]

Anyone else ever run into this. I have noticed it only does this on ac. Blowing in fresh air or heat it never does it. Only when ac is on.

 

[osgprometheus]

Damn... That's a good one. Let me ask my buddy and see if he has got something.

 

[RayVoy]

Anyone else ever run into this. I have noticed it only does this on ac. Blowing in fresh air or heat it never does it. Only when ac is on.

Hmmm, ok, it worked fine over the winter. It has to be something in the mode switching. Does it act just like you manually selected the defrost?

Possibly in the control unit in the dash, or (and by not being there, I can only guess), the connector to the control unit.

If there is a moisture sensor (to tell the control unit the windshield is wet), perhaps it is faulty.

 

[black07sierra]

Only does it in auto ac mode. Still shows vents after it switches to defrost. I can't change it back manually. I have to shut off the truck and when I turn it back on it works fine until it decides to do it again.

 

[black07sierra]

Bought another control module on eBay. Gonna try it. Hopefully that is the problem.