Recently, with the extreme temps down here in Texas this summer, my 2004 Silverado with dual climate control has been acting up. The air will usually blow fine in the mornings when it's still somewhat cool outside. During the rest of the day, the air on the drivers side will suddenly blow hot as can be. The only fix for it is to restart the truck, which only fixes it for awhile. This happens constantly every day. I heard something about a blend door or an actuator or something, not sure. Was wondering if anyone can confirm this and possibly give me a part number on it. The dealership quoted me $300 for the part, and wasn't even sure if this was the problem.

Any advice or help would be appreciated.