hey everybody, i own a 2004 tahoe LT my heater comes on while the a/c is blowing , the truck has individual climate control for driver side and passenger side while the driver side is blowing cold it suddenly blows out heat and the passenger side stays cold . if i turn the whole a/c system off it does not reset i have to turn the whole truck off for it to blow cold again, any body know the reason for this or any ideas? thnks