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It is called condensation, warm and humid inside, cooler outside.

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Q: Why do car windows fog up when the heat is not on?
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Why do car windows fog up?

well it could be because of the heat. if its cold out and you have the heat on in the car, then you will get hot and that will cause the window to fog.

Why do brand new car windows fog up inside in cold weather?

Windows fog because the glass is cold and the humidity is high inside the car. It has nothing to do with the age of the car. Try turning the fan up to circulate the air better, and if that doesn't work, turn the AC on -- but turn the heat up so it doesn't get cold. That will do it for sure.

Why do car windows fog up in winter?

moisture from your breathing for example condensing on the cold glass

Will the blend door failure cause windows to fog in a car?

No the blend door not functioning will not cause fog; it may however prevent the windows from being defogged or defrosted. If the widows only fog up when the defroster is on, then you either have a coolant leak in the heater core or your air conditioner compressor isn't working (the AC is used to dry the air when the heat is on).

What would cause the windows on a 2003 Windstar to fog up in cold weather with the heat on?

Any type of moisture including your breath.

Why do windows fog up in 2001 Chevy Malibu heater core has been checked is OK?

If the heater core is ok, check to insure your ac unit is working. The ac works in conjunction with the heat when running defrost, and without the ac air windows will fog up .

Why do car windows fog up when making out?

Two people, breathing heavily. There's a lot of water vapor in your breath, and when two people are going at it they breathe a lot more causing more water. If it's cold outside, the windows fog up like crazy.

How do i clear steamed up car windows?

Rub them with soap then clear the soap of with a cloth or paper this will reduce the amount it wil fog in the future as well.

Why do cars warm up when there closed?

Cars warm up to a temperature higher than the surroundings because of the glass in the car windows. This is called the greenhouse effect. High-energy heat waves from the sun are able to pass through the glass of the windows, and this energy is absorbed by the materials inside the car, causing it to heat up. The glass does not let the less energetic heat waves being let off by the warm car pass through the windows. Therefore the heat is "trapped" inside the car, causing it to get warmer than the surroundings.

I have a 1992 Chevy blazer my air works but my heat doesnt....i hear the fan blowing but no heat comes in?

If your windows fog up you thermostat may not register because you heater coil may be broken.

What is the time table for removing and installing a heater core for a 1992 cadillac deville?

It will fog up with moisture, the inside windows in the car, also accompanied with the sweet odor of coolant.

Why do the windows fog up in a 1993 buick regal?

1. No heat coming out of the defrost duct or wrong heat selection position. 2. fresh air intake blocked or dash switch in the recirculating air position. 3. Heater core is bad if there is an antifreeze smell in the car or antifreeze is coming out the heater lower ducts or on the floor. 4. If car is equipped with internal heat control valve, the valve may be leaking.