Thermostat problems on 2007 GMC Yukon XL Denali

Rookie cbe0621eac06868b3efe0d8d1d3611e23c60d3114864ea2ec19a68cfbd3eebab
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.
(1) Answer
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.