I have a 97 grand caravan w/187K miles. One annoying thing that I notice with my van is that every winter, when I use the heater, the windows fog up bad. Have to use the defrost alot to remove the moisture from the windows just to see. It is not the heater core as I do not lose any coolant, and there is no smell associated with it. Where is this moisture coming from and how do I correct it?

 

A possibility:
If you have your air handler control on bilevel setting. (dash and ground blowers)
With the heater on.
It will activate the air conditioners compressor to cycle.
That will send cold air to the windshield. Making fog in the lower middle center of the windshield.
Try putting it on floor heat or windshield defrost, Only.

Hope that's it.
Tom

 

No that isnt it.

Whenever I have the floor heater on, or the vent on (AC is off), and it is cold outside, the inside windows get fogged up - lots of moisture. If I turn on the AC (the bi-level that you mentioned), even with the heat on, the moisture goes away. But I am not losing any coolant and I never smell the sweet smell of coolant, so it cant be coolant leak in the heater core. Any advice?