Why won't my windows defrost in the cold?

Dear Car Talk

Dear Car Talk | Apr 01, 1990

Dear Tom and Ray:

I have 1986 Toyota Cressida. It's a fine car except that when it gets cold and rains or snows, the inside of the my windows fog or ice up. What's wrong?

RAY: Well, my first guess is that you forgot to close the sunroof last fall, but I'll assume your mechanic has already checked that.

TOM: Actually, Wilson, it may just be that you're not turning on your air conditioner when you use the defroster. In many cars, these switches are integrated, but not in your Cressida. Many people don't realize that the "conditioning" in air conditioning is the removal of moisture from the air. If the moisture is not removed, it ends up condensing and freezing on the insides of your windows.

RAY: That doesn't mean you have to shiver all winter. Just set the selector on "defrost," push the heat selector all the way to "hot," set the fresh/recirculate switch to "fresh," and turn on the Air Conditioner. What you'll get is fresh, warm, dry air, which should clear the windows.

TOM: If that doesn't work, Wilson, getting a scraper and some artificial flavorings and start selling Italian ice to the neighborhood kids.

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