My '98 Dakota has begun putting out a small amount of smoke from the heat/AC vents. It is not noticeable when the fan is running, only when the ventilation system is off. I notice that it seems to be directly related to the heat up of the engine coolant - as it does not appear unitl the temp. indicator on the instrument cluster is about 130 deg. It is definitely not vapor - but actually smoke; smells like something is overheating (but not a coolant smell). Any ideas??

 

I would say possibly leavesor other debrisin the heater box have come in contact with the blower motor speed resister, but you say its not doing it when you run the fan?
When you pop the hood, is there smoke visable?

 

Topic Re-visited. Actually, after watching this for a while I now believe it may be steam instead of smoke. On a cold start w/ AC running - no visible 'stuff' out of ventss As soon as the engine temp begins to reach normal running temp, I begin to see & smell 'stuff' coming out of the vents. Is it possible that the condensation drain line has plugged, backing up condensation in the heater box, and the heater core is sitting in water, which it begins to vaporize as temp comes up? - Its definitely not a coolant leak - radiator levels have remained normal now for cuple months.

Any new thoughts appreciated!!

Wally