I have a 2001 Dodge Ram 1500 with a V6 engine. When I adjust the temperature on the air conditioner the unit suddenly goes from all cold to all hot. There is no "in between". I guess that it is a blend issue, but am not sure where to start.

 

Yeah i am kid of, sort of, in the same boat. In addition to what your are describing, when i hit the brakes a bit too hard, not necessarily a panic stop, my cold AC air all of a sudden goes to full warm. I turn off the AC for thirty seconds, back on, and it's back to normal. I have made sure that my check valves and vacuum lines are hooked up properly cause i have had the wild vents in the past. But aside from that don't know what to do either. I am starting to think it's the AC control unit. Mine is also a 2001.

 

Likely the coupler (interposer) between the little stepper motor, and the blend door axle is broken. You can find the motor on the bottom of the heater box, passenger side, just above the trans tunnel. It's held in by two screws, one of which is rather fun to get to. (notching the carpet a bit makes it easier.) Do a search on "HeaterTreater", they have nice pics of everything.