2005 Sierra Denali has dual controls for driver/passenger - when the truck is first turned on, cold air will blow, then it will automatically go to heat. I have to ...

when the truck is first turned on, cold air will blow, then it will automatically go to heat. I have to stop and turn the ignition off and restart to get the ac to resume. Is there a simple fix to this problem?

Does your a/c light turn off as well, or do you mean it blows hot air when its still set to cool. Trying to find out if its your controls or mechanical...

That sounds like your blending door is about to quit...it's behind the dash on the passenger side. It controls whether to blow hot or cold air.

The Dr. is correct (lol i hardly ever get to say that lol) The blender actuator is bad. There are 2 different ones. The dealership has a program to scan codes to figure out which one is bad. But they are both very pricey to fix. they are back behind the dash and airbag in the passenger side, and somewhere behind the dash on the drivers side. I just had mine fixed last week, if i could find my receipt i would let u know the rough cost but i cant find it.

my truck does the same thing on the driver side but only when i had the "AUTO" on, if I ran in manual I didn't have any problems. Just replaced blend door actuator on my wife's impala ss this past summer and it was all for not. Her's was/is in the climate control unit.