I can't turn down the heat in my truck,, turn the **** all the way to cool and it stays on heat,,, Even with AC on full,,, still heat. Is this a thermostat problem (dosen't feel that way) or maybe the rheostat in the dashboard has failed. Any knowledge on the subject??

 

Sounds like the switch. Not to expensive and pretty simple to replace.

 

Pull the **** off the stem that goes into the switch then look at the back. These had a habit if striping out and when that happens the **** turns, but the rod that goes into the temp switch doesn't turn. You can check by turning gently with a plyers once the **** has been pulled off.

 

I agree that this is the likely cause. I'll just add that you can swap the **** with one of the others and it should fix the problem. (for some r

 

if the **** checks out o.k..... it controls a temp door (blend door) that is motor operated. It sets in the hot air duct above trans hump under the radio. Take off the plastic dash above the transmission hump and you can see the motor and cam/ rod that move the door--- motor failed or cam broke.