2000 GMC Yukon Denali front AC blows hot air while rear blows cold

On all Yukons, Tahoes or Suburbans have two AC systems. The back system has two boxes on it, and the very first one is the one you need to replace. It controls the system to open and close the heat port on the system. If it's closed it'll only blow cold, if it's open it'll only blow hot. You can take it off and manually open it, but when summer rolls around you'll have to do it again and close it. I'll post a link from YouTube later that shows exactly what I'm talking about. Hope this helps. OK everyone, here's the link to what I'm talking about: http://m.youtube.com/watch?v=y4-WlE6-Nkc

I have the same year, same model, and now the same exact problem!

i have the same problem except it in a 1999 mercurey villager

American made garbage. Should have bought foreign!

I also have this problem. I asked the dealership about it, and they wanted a $70 diagnostic fee to look at it. They said they $70 would be credited to me on the repair bill if I decided to have them fix it. But, I don't wanna pay for them to guess if they cant find out for sure. Will anyone's dealer give them a free look/ advice?

My post above. Just signed up to receive emails if anyone else has any input. :)

I have a 2004 GMC Yukon XL that the front blows cool air then it gets hot and goes back. The back air is working great, but it is a separate unit. The dealer recharged the system 2 weeks ago for $140 and now it is back today because it just isn't right. It has to have something to to with the compressor kicking in or a relay. I still have an extended warranty on it and they need to figure out why this is happening so it can be covered and repaired or replaced.

I have a Buick Lesabre that blows cold on the passenger side, and hot on the drivers side. I would like to follow this question it may be related to my Buick issue

I wish I had the answer I have a 1999 Yukon Denali and the exact thing is happening to me. Warm in front, cool in back. Please post any answers as I would like to know as well.

My 04 silverado starts off cold on both sides then sometimes the driver side vents will blow hot air. when we stop and turn off truck and start it up and it is fine again. Could it be the thermostat for that side not working??? anyone have any answers for this problem?