Calling all A/C gurus out there

I believe the potentiometer in the control knob tends to go bad and cause the blend door to randomly move to hot, all the FSM testing attached below.

 

Thanks for this. I think this is EXACTLY what I needed. I will be testing the controls this weekend now that I have a procedure. I’m leaning towards the control being bed being that the blend door bench tested 100%. The random switching to heat seems to be affected by changing fan speed but turning the temp knob to max heat and then all the way back to max cold makes it go cold again. Also to reiterate a statement I made wayyyy earlier in this thread, the heat in the winter seems to be all or nothing. Turning the temp knob slowly down from max heat has no effect until it eventually hits a point where it goes cold (usually around the middle of the knob range) point is, there’s no “half heat” if you will.