Heat only works on high in my Caravan HOW DO I.

Hi Kford1,
I have had this problem in a Chrysler Cirrus, twice in my wife's Sebring and once in my Caravan. The resistor pack that is installed in the vehicle has been modified I have been told by a service manager. They are reasonably easy to change and I paid $51 Canadian at a dealer for the last new one that I bought. The resistor pack is above the foot well on the passenger side, behind the noise baffle.

I experienced the same symptoms in my 99 Intrepid. A new resistor pack was installed but the problem returned.
After diagnostic, it was the actual blower motor. It was outputing to many amps and that is what caused the resistor pack to fail. After the motor was replaced all is fine, about a year ago now.