I have a 2001 3500 RAM turbo diesel dually with heat/AC problems. I don't think it's the blend door because I have heat and A/C. The problem is it's either unbearably hot or freezing cold nothing in between, no control. Does the climate control cover on the dash just pop out or are screws holding it?

Cheers, Miles

 

Sounds like the coupler on the blend door motor has fractured, and so you only get the two extremes. Easy to check, the motor is under the dash, bottom of the heater box, just to the passenger side of the trans tunnel. Held in by two screws. (one of which is rather a pain to get to.....) Have a look, see what ya find.