Rear Climate Control

[wcrayner5]

I have a 2004 Yukon Denali which seems to only blow cool air from the rear vents. I can change the temp from either the driver overhead console controls or the rear passenger controls and the temp never seems to change. The driver and passenger controls work fine.

[GM-Tech]

The first step would be to go to the back and feel both heater hoses to make sure hot water is actually circulating through the heater core. This would be an unusual failure, but entirely possible.

 

You could also have a bad temp actuator in the rear unit. This would need a little diagnosis and a scanner would help a lot.