I have a 2011 Silverado with dual climate control. The passenger side will not blow hot when the heat is on. It blows cold continuously whether the dual climate is activated or not. I'm not sure what could cause this. Maybe a blend door actuator or something? If I turn the engine off and back on it will sometimes blow hot after that. Even after that it sometimes will quit blowing hot and turn back to blowing cold. Any ideas? Im pretty sure its still under warranty. I will be contacting the dealership tomorrow to find out.