Ac/heater issue

[Chrobertaz]

Hi everyone, my wife and I bought an 04 Yukon Slt last week and are loving it. We didn't catch this when we test drove it but the Dual Climate control doesn't let us adjust the temp to hot. It's the digital unit and when you try to turn it to heat it will go up a few degrees then jump back down to 60 degrees. It does this on both sides. I tried the reset with turning it to Auto and pulling the fuse etc. All it did was set the temp to 74. Then you go to adjust the temp again and it drops down to 60. It blows the temp it says it is. This makes me think that the actual unit is bad. Am I off base here? Not real sure where to start.

We in Phoenix and it's still 95 degrees so we're not desperate yet. Thanks in advance