Fogging Windshield - Winter

[boothgolf]

My wifes's '94 325i convertible has started to completely fog the windshield when she puts on the defrost, (winter driving). It is so bad that she can not see. I'm obviously concerned, does anyone have an idea?

[Bimrpwr]

i have the same issue sometimes...but it is due to the window being dirty, once i clean it it is good for awhile..i am sure there is another reason for it happening..the the coldness of the air blowing out compared to how cold the window is

[JuBu]

Same thing occurs in my '95 M3...Once I clean it, it seems like the vents have an easier time defogging the windshield, but it still fogs up nonetheless. This does not happen at all in my '97 328, which leads me to believe that air from the outside is somehow getting into the car, leading to the condesation issue.

Until I give it a very thorough cleaning, I guess I can't confirm that it's not jsut due to dirt, but I'm leaning towards an air leak of some sort.

[perlman]

i have a similar problem with my 1989 525 and i think it comes from outside air mentioned above. For some reason, my windshield since replaced never seems to have sealed right, so may want to think about resealing your windshield if cleaning doesn't do the trick

[Bimrpwr]

well on the 89 i cant remember if it did it b4 the window was replaced,,but i know it does it after it was repalced and the auto glass guy said that BMW doesnt use any silicone for the windows that the rubber seal that goes around the window is good enough for them...so maybe some air could be coming in from around there

[Ronnaferd]

put some rain-x on there....but make sure you get the kind that is for INTERIOR not exterior. That seems to work pretty good for preventing fogging Buy Rain-x here (http://www.theconsumerlink.com/RainX/detail/TCL+AF21212/11)

[Rickman]

An old trick to stop the fog is to turn on the aircon as well as the demist, or just turn on the aircon to the windscreen area. A friend showed me and it clears the windscreen much quicker. Don't know whether demist turns on the aircon as well, but don't think it does on my car anyway. Hope this helps.

[squirtdad]

I second rickman....just had to do that today......started raining, put on the defrost..and then needed to turn on the AC to get it to clear up.

It seems be determined by a mix of inside/outside temps, humidity, etc