GMC Repair: AC, gmc yukon, flood gate

Question
I have a 2002 GMC Yukon. The top ac vents are blowing cold, but the main vents in the front driver and passenger side are blowing warm. How many places does a 2002 Yukon have to ad freon and where is it? Why would the backseat vents in the roof be blowing cold and the fronts blowing hot? Thank you for your assistance.

Answer
it sounds like the stop/start control module is starting to go out or the vacuum switch is not working properly. I would replace the switch on the dash. if it is still happening replace the control module.

the reason you are getting hot and cold is that the a/c and heat control work like a flood gate, if you will. It work off of vacuum produced by the engine. there is a control module located near or at the blower housing. it is located on the outside. if the block off (door that seperates the hot/cold side) is not opening or closing all the way you will get these results.