Today while I was driving my 2004 Yukon XL the A/C was blowing ice cold and working correctly. Then all the sudden the two driver vents(the vent right next to the CD player, and the vent on the left side of the steering wheel) started blowing hot air. It was like the heater was on, the air it was blowing was hotter than the outside air. I reached over and checked the two passenger vents that are both beside the passenger airbag and they were still blowing cold. I made it to the place I was driving to and was there about 45 mins and when I got back in my car and started to drive back home the air was working correctly blowing cold. What could be causing this? Is it an actuator going bad? Thanks for your help guys.