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The Ultimate Guide on How to Defog Windows in Your Car

defog windows

Other than aggressive drivers and traffic jams, it’s hard to name something more annoying than figuring out how to defog windows during a long commute.

Window fog makes it hard to see the road ahead, and like a pesky bee to a soda can, it always comes back.

Fortunately, car experts have clearing foggy car windows down to a science. Keep reading for advice on how to defog windows and tips for making it happen faster.

How to Defog Windows on a Cold Day

The fog that forms on a windshield is condensation, created when water vapor in the air near the glass falls below or above a certain temperature, known as the dewpoint. When the temperature of a car cabin gets warmer than it is outside, that’s when the moisture from our breath and clothes condenses on the inside of the windshield and windows.

When the windshield gets foggy, the go-to move for many drivers is to blast the defroster, using the hottest heat and strongest setting to clear the glass. The warm air from the defroster helps evaporate the moisture near the windshield, but it’s only a temporary fix.

If you want to stop the fog from forming, experts recommend using cool air to lower the temperature on the inside of the glass. You can accomplish this by blowing cool air out of the defroster, turning on the air conditioner (which acts as a dehumidifier) or by cracking the windows, if you can tolerate a brief face-full of cold air.

John Paul, AAA’s Car Doctor, recommends turning off your car’s “recirculate” button (symbolized by a car with a looping arrow inside). When it’s off, the car pulls in dry air from outside the car to clear the windshield, instead of using moist air inside the car, which causes the problem in the first place.

“The other issue that causes moisture on the inside of the car is damp carpets,” Paul said. “It is always a good idea to wet-vac the car after a week of getting in and out of the car with snowy boots.”

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How to Defog Windows on a Warm Day

Getting rid of fog on the outside of the windshield when you’re running the A/C in the spring is much easier – just use your wiper blades. Get tips on how to make your windshield wipers last.

But if the humidity outside the car is causing the side windows to fog up, try using the opposite logic of what to do on a cold day. That is, use warm air, or the least-powerful cooling setting, to raise the temperature inside the cabin a little bit. That way you’re not putting the windows up and down every five minutes or turning the wiper blades off and on the entire trip.

Other Tips and Tricks for Foggy Car Windows

Cleaning the inside of your windshield will help prevent fog before it happens, said AAA Northeast spokesman Robert Sinclair Jr. Fog has a harder time forming on a clean surface, and an easier time forming on dirt and the film left behind from smoking, so he recommends taking a couple minutes over the weekend to spruce it up. Use a non-sudsing ammonia for the best clean, he said (just make sure to crack the windows open while you do it so you don’t inhale the stuff).

Another, more unusual tip, comes from YouTuber DaveHax, who recommends keeping a sock full of kitty litter on or close to the dashboard. The litter is very absorbent, and can help contain some of the moisture in the cabin.

Also, keep wet belongings like a recently used umbrella or sweaty gym clothes in the trunk if you want to cut down on the amount of moisture inside your car (hey, every little bit helps).

What Not to Do

Lastly, most people know this, but it bears repeating: Avoid wiping foggy car windows with your hands. Hands carry oils that will transfer to the glass, so while it could temporarily defog car windows, it might just make the problem worse later on. Keep a microfiber cloth inside your vehicle in case you have to clear the windshield in a pinch.

And when you clean your windshield, avoid spraying a cleaning product directly on it – where it will splash on the dashboard and elsewhere. Spray your solution on a microfiber towel, and wipe up and down, and side to side, using long stokes. Then use another towel to wipe off any excess spray.

Now that you know how to defog windows, you’ll know what to do the next time things get steamy inside your car.

Do you have any tips or questions about defogging car windows? Leave them in the comments below. 

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11 Thoughts on “The Ultimate Guide on How to Defog Windows in Your Car

  1. I’ve always been told to try RainX, but maybe that’s just on the outside of the windshield. Also I know that there’s a product called The Original Bee’s Wax Old Formula Furniture Polish. I use it to clean glass, stainless steel, wood, porcelain, marble really just about ANYTHING! And when you use it on glass, it helps a lot with fogging. We use it on our bathroom mirrors and they don’t fog when we take a bath/shower! Plus when KIDS (or adult HUSBANDS!) touch the glass or mirrors it doesn’t leave fingerprints!!! I love the stuff! You can get it on Amazon of course! But I got mine from an Amish store near Shipshewana.

  2. been doing this for years),is to turn on the air conditioner(regardless of the season), set the temperature you want and turn on recirculate(not off, but on). The air conditioning coil will remove all the moisture in the car so there is nothing left to form on the windows.

  3. One essential tip is to ensure that the fresh air/recirculated air control is set to fresh air. Otherwise, especially if the AC compressor is turned off, moisture radiating from the occupant(s) will condense on the cooler glass causing them to fog up.

  4. Another neat trick ofor those of use that tirie of windows fogging up all the time. Clean the inside of all your car windows with a can of cheap foaming traditional shaving cream and a soft cloth. Wipe till dry, using another clean cloth to really finish it off. The you’ll be amazed at the lack of fogged up wontiows in the future! Barabsol is awesome ????

  5. Yes it would be nice if the “experts”allowed you to control the air conditioning system. Most defrosters default the AC on which can be less than ideal in some conditions.
    Some less automated systems can be cheated by leaving the fan off with heat and defrost on.

    1. You can buy anti-fogging solution at an auto parts store. It’s effective but it scatters light. Don’t use it on your windshield, or you will be bothered by glare at night, but it’s very useful on the inside of side windows. Most defrosting vents don’t do a good job of drying those anyway.

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