Originally Posted by NJspeed69
I'd say if you don't know the source of moisture, try blowing the AC until the fog disappears, then put on the heat. If it keeps reoccuring, it could be something with your car. Water in the vents? I dont know. But theres probably a moisture source somewhere.
The first time I had this severe problem I started out after the car had been sitting outside for a full day and I immediately turned up the defrost with a/c on full blast. The air at that point was still cold. That's when the windshield fogged up. Only after some warm air came out of the vent it started clearing it...but not very much. The next day I left the air cold and it was fine for a little bit but then when I turned it up a bit ( since it was quite cold 28 F!) then the fogging came back. I really don't want to be frozen by the time I get home...oh but I did have the heated seat on.
As for the rain-ex, I still have some in my garage from a few years ago when I tried it on my Sebring. Got terrible results with that. It made the grime on the windshield only worse. But maybe i just used too much.
Anyway I'm gonna try some of those suggestions again this weekend. Maybe i just missed something.