Yesterday while driving my 04 silverado the drivers side only started blowing hot air. passenger side was cold. The truck has the dual zone A/C set up. At the next light I shut off then restarted the truck and it started blowing cold again. I have had this truck since it was new nothing has been changed or modified or added. What Happened? Help!. I live in central florida, it's hot down here!

 

I would suspect the blend door is sticking, the door that controls the amount of hot air that is allowed into the passenger compartment for the passenger side or drivers side

 

Thank you. Do you or anyone else know where i could find a drawing or instructions on where the blend door is located and how to replace it? Oh I do not have the digital climate control system just the standard dual zone set up.