Possible A/c Sensor Problem?

[smithran]

I have an intermittent problem with the A/C in my 2004 Yukon Denali. The A/C for the most part runs fine. It gets good and cold. Once in a while it will just start blowing out hot air out of the main vents on the drivers side only when the a/c is on. I cannot just turn it off either. If I turn off the A/C with the controls and stop air from flowing out the main vents, it will blow out vent in the floor. The only way to reset this is to pull over and turn the engine completely off.

 

 

Anyone have any ideas?