Dodge (for my 2003 at least) uses "blind" motors to position the doors that count motor pulses. From time to time the computer runs the doors to the stops to calibrate them. Eventually something goes "SNAP!" during the calibration process of full power on the stops and a blend door is busted. Not sure when they quit using vacuum for the doors. You may be having to track down an electric or mechanical vac pump.
I’ve been putting off replacing the heater core in Red Ryder (a ’98 Dodge Turbo Diesel) for a lot longer than I should have. I’ve been keeping a car blanket in the cab during the winter for a few years now. It generally takes about 30 miles at highway speed to bring the cab to a comfortable...
Aftermarket metal doors are out there. I tried HeaterTreater blend doors and the heater never worked evenly passenger to driver side. Shop that did the work wasn't exactly grade A either. Eh, BFD in Phoenix.