I have the temperature set the same on driver side and passenger side and the cooling setting is on "auto". Heat is blowing out of the driver side vents and cold air is blowing out of the passenger side vents (Note it's 90 degrees outside and I'm trying to cool the interior). Lowering the driver side temp setting does not change the output.
Thermostat problems on 2007 GMC Yukon XL Denali
by cfh in Bristol, VA on September 13, 2009
ANSWER by Oakman , September 18, 2009
The dual A/C in your 2007 GMC Yukon Denali has one temperature control door and actuator for the drivers side and another for the passenger side. It sounds like the passenger side is working OK but the drivers side is stuck in the heat position. If this is the case there should be a fault code stored in the A/C module. Any stored fault codes can be read with a scan tool and would help diagnose the fault with your A/C system. If there is indeed a fault code stored for the drivers side temp door chances are the actuator will need to be replaced.