I kinda have the same sort of problem. I have a 2004 Pacifica and my problem is that the only speed I get from the unit is low. But when I turn the ac/heater off the fan blows high???? This also happens when turning off car to get out. Once key out of ignition but before I open door the fan blows on high??
Where is this resistor that you talk of?? All I can find info on is the relay that may be the problem or the power module or the motor itself.