I have a 2005 Hummer H2 SUT and it has been great so far but the other day the driver side dial of the thermostat messed up. The passenger side will get hot or cold but the driver side stays blowing cold air regardless of what temp I set the dial too. It the whole module messed up or is there a valve that is no long working on the controls? Help!

 

You should read the blend door thread. I bet your issue is covered in there.