Hvac Control Issue

[LS1_Silverado]

2006 GMC Sierra SLE with manual dual zone climate control (not electronic). At any given time while driving it will go to full heating mode regardless if it was set to A/C. Hot air will come out of whatever vent is active at the time. The only way to reset is to shut the truck off and restart it. This is random and could happen twice an hour, three times or not at all. There is nothing wrong with the A/C it blows very cold when this problem is not occurring. Any help would be appreciated, TIA.

[jrrod2004]

2006 GMC Sierra SLE with manual dual zone climate control (not electronic). At any given time while driving it will go to full heating mode regardless if it was set to A/C. Hot air will come out of whatever vent is active at the time. The only way to reset is to shut the truck off and restart it. This is random and could happen twice an hour, three times or not at all. There is nothing wrong with the A/C it blows very cold when this problem is not occurring. Any help would be appreciated, TIA.

 

 

Had this happen to my truck. Dealership determined that the HVAC unit was "shorted" on the control board so they replaced the HVAC controller under warranty and it fixed the issue.

 

 

 

EDIT: The controller is integrated into the unit that you use to control the fan speed, temp, zone...not sure if you were aware of that.

[jrrod2004]

06/19/2007 805 04 # D0362 - HEATER AND AIR CONDITIONING CONTROL REPLACEMENT 15832317 - CONTROL

 

That was the line item that was on the warranty work order...

 

 

 

 

Here is a link for the part:

http://www.rmsautoparts.com/proddetail.php?prod=15-73504

 

 

Estimated Total for the Part (with Shipping is): $137.43

[tramz]

Mine started doing this about a year ago, has happened three times since the first time. Ah, the first time, Driving down the road having alittle tiff with the wife, and all of a sudden, HOT air on her side..She thought I did it on purpose.....couldn't turn the heat off, she's bi%$hing, I'm LMAO... That was a fun afternoon.

[jrrod2004]

Mine started doing this about a year ago, has happened three times since the first time. Ah, the first time, Driving down the road having alittle tiff with the wife, and all of a sudden, HOT air on her side..She thought I did it on purpose.....couldn't turn the heat off, she's bi%$hing, I'm LMAO... That was a fun afternoon.

 

Thats funny...and it happened right at the time that you needed it

[LS1_Silverado]

Thanks guys, I'm in Canada so the price for that part is considerably more . I'll do some more research before I go throwing parts at it! Is that the module that controls all the HVAC motors as well,(Right/ left temp, mode and recirculation) or is there another module that is linked to the "head unit"? I have a FSM diagram but it is spread over acouple of pages so it gets a bit confusing, though it looks like there is just the one module. I was expecting a "computer" box under the dash somewhere.

[jrrod2004]

Thanks guys, I'm in Canada so the price for that part is considerably more . I'll do some more research before I go throwing parts at it! Is that the module that controls all the HVAC motors as well,(Right/ left temp, mode and recirculation) or is there another module that is linked to the "head unit"? I have a FSM diagram but it is spread over acouple of pages so it gets a bit confusing, though it looks like there is just the one module. I was expecting a "computer" box under the dash somewhere.

 

 

nope, all integrated. when you pop off the HVAC user controller, if you look at the back, you will see the circuitry...I will see if I could take some pics of what I am talking about either later today or tomorrow...

[tramz]

Try Ebay, I found mine there for less than $60 with shipping and looks brand new and so far no issue (and no burned out bulbs). You may get lucky.

[Sir Dan]

Not sure if this would be relevent to your problem, but on my '05 I had this happen but that was equipped with auto climate controls,...very similar symptoms tho. They fixed the problem by using a Tech 2 to go in and update or reprogram the BCM (computer box) software. Maybe it would be cheaper to just call the dealer and ask if they can take a look at it before you start throwing money at parts.