I've got a problem with the air distribution on the front HVAC control, it wont
switch to the floor ducts when switched to heater, and in other modes it always blows out of the dash vents. Do I need a DRB-III to check this out?
This is a 2001 Durango. I also can't get any heat from the rear heater. Thanks for any help.

 

Check your vacuum line going to the HVAC box to make sure it has broken. As far as the rear heat try flushing the core it sounds like it's plugged.

 

The problem is fixed, at least for now, I located the MODE DOOR ACTUATOR, which rotates a wheel to which linkages from the VENT DOOR, HEATER and the DEFROST doors
are attached to. I removed the actuator and the wheel and found that the vent door was sticking. I moved it through it's range of travel several times until it freed up, reassembled everything, and it's been fine for a week now. Thanks for the responses.