Myheater/A/C either runs at cold or hot with no in between temperature. If the control **** isturned from full cold on the left to a moderate temp to the right, it will just blow hot air. What and where do you suppose is the source of this control failure?

 

Sounds like your blend door is sticking. It is either open or shut--no inbetween. Do you get any popping sound when changing from cold to hot? Take the glove box out and the blend door is right behind. Make sure it is working and still connected to the actuator.
WC

 

Thanks, Wayne. I'll check it out. Last time my A/Cstarted blowing hot air I did hear a pop.