GM-GMC: 2004 GMC pickup heater/air conditioner, gmc pickup, ac system

Question
The heat/ac system is the led display type with "auto" setting. Is there a sensor for each side or is the "controller" faulty? It switches back and forth from heat to cool on the drivers side only-passenger side is fine. If there's a sensor, where is it or if it's the controller, any tricks to replacing? Thank you

Answer
There should be a sensor located in the duct on the drivers side that indicates the temp of the air blowing out that vent.  In order to diagnose that properly you would need a scanner and need to look at the temp that is being displayed by that sensor.  If the temp looks ok but the controller is still cycling from hot to cold it is likely the controller, if the temp looks like it is out to lunch, it is likely the sensor.  I have seen plenty of both.  If you were going to make a guess, the sensor is cheaper.
Hope this helps