John R: I have a 2003 Chevy Tahoe V8 5.3 liter.
I am having issues with my dual automatic climate control with temperature knobs on both sides. When adjusting the temperature knobs they don’t respond correctly. For example, turning the temperature knobs to raise temp it goes down and vise versa. Almost like stripped but not. Also when I have temperature on 80 degrees it starts off hot then after a minute or two gets air gets cooler even when at 80 degrees still. It only stays hot when on max 90 degrees.
Sparky: The knob adjustment issue is inside the control panel and is caused by non use. Sometimes all it takes is moving the knobs back and forth repeatedly to clear up the internal contact areas. If that does not work the control panel will need to be replaced.
The lack of heat issue can be caused by something as simple as low engine coolant level. Other causes would be faulty temperature sensors, doors, actuators and control systems. Other than a coolant level check the only things that can really be checked without a scan tool are the temperature reading on the rear view mirror, visually inspecting the temperature door movements and listening to the interior air temperature sensor above the driver’s head. You can also place a very light piece of paper over that vent and see if it will pull the paper up to the grill.