Sorry I was trying to move it to chevy experts before answering, but i messed it up.
It sounds like the temp blend door motor is bad on that side, but firts try to recalibrate them. If you have automatic temp control clich here
, if not click here
Do you have a scanner to check for climate control codes? If you don't then you will have to manually check the drivers side temp door motor.
The procedure to get to the motor is here
1. Install a scanner and check for codes in the Heater Ventilation and Air Conditioning (HVAC) system.
2. If the scanner does not have the ability to get into HVAC system, then use a voltmeter to check the feedback from the temperature motor.
3. Back probe the Dark Blue wire at the right temperature motor and make sure the voltage is in the range of 0.5-4.5 volts.
4. If voltage is above or below that specification, then replace the temperature motor and disconnect the battery to reset the system
Do not plug a new motor in and let it hang to check operation. It must be hooked to the HVAC box or it will not work correctly
You may need to pull the havc module to get to the motor to test it, and that will take
let me know if I can help further.