I have recently purchased a 1999 Durango, and after a few days noticed the heater does not work. If the dial is turned to heat on my panel, I have also noticed a white mist coming out of the vents. There is no smell, and the floorboards are not wet. It almost always only happens when the dial is turned to heat (the a/c works fine), but occasionally it will also happen when idling at a stoplight or stop sign. Any ideas of what this may indicate?

 

Check the coolant level first and foremost.

Next you could have a bad heater core.