No rear heat

[AZI]

Just noticed that rear heat will not work in my 04 Denali. Heat in the front is working properly, but when i try to turn the heat in the back, there is nothing but cold air coming out. I adjusted the temperature, plus tried to conttrol it from both front control panel and the rear one, but still no luck. Does anyone know what that could be?
thx

[bsweasel]

check my post in the tahoe forum. I'm in the middle of solving the same problem. I'm getting close.