Maintaining good visibility is one of the most important elements of safe driving. That means paying extra-close attention to your windshield by replacing worn wipers to combat rainstorms and clearing away ice and snow in the winter.
But there’s one more windshield-related problem that can appear in an instant: fog. Depending on the weather conditions, it’s possible for your entire windshield to become foggy in a matter of seconds. That’s why it’s important to learn how to defog your windshield – and fast.
Why does my windshield fog?
A car windshield fogs when there’s a significant difference between the temperature and moisture content of the air inside and outside your vehicle.
Here’s why: Cold air does not retain as much moisture as warm air. That means if it’s cold outside, then the warm air inside your car likely contains more moisture – and things can fog up even quicker with your breathing or a steaming hot cup of coffee.
That’s why condensation, or fog, forms on the inside of your windshield – because the air immediately surrounding the glass is colder than the rest of the air inside your vehicle.
How can I defog my windshield?
Try these quick tricks.
Use the “defrost” mode. Most newer vehicles have a specific button or climate control setting to defog the windshield. The icon for this defrost mode will look like some variation of a windshield with arrows pointing up through it. There may be a separate button to activate the rear window defroster, too.
When you use this setting, your car will automatically turn on the air conditioning and direct warm, dry air up toward the windshield.
Manually adjust your climate settings. If your car doesn’t have a defrost mode, or it doesn’t seem to be working fast enough, try manually adjusting your climate control settings. To help settle the debate on which settings work best, YouTuber and former NASA engineer Mark Rober conducted his own experiments. Here’s his recommendation:
Turn up the heat. Set your heat to high and turn the defroster fan up to its highest speed.
Turn on the A/C. It may seem counterintuitive to turn the heat on high and turn on the air conditioning. But your air conditioning system will remove humidity from the air coming through your vents.
Turn off air recirculation. The icon for this button probably looks like a U-turn arrow inside an outline of your vehicle. When it’s on, the car will recirculate the warm air inside your vehicle through the vents. But when you turn it off, it allows your car to draw the cold, dry air from outside to aid in your defogging efforts.
Crack your windows. By letting the outside air enter your car, you can quickly reduce the humidity of the air inside the cabin. If it’s extremely cold or rainy, it’s worth toughing it out – even cracking your windows for a few seconds could help the fog clear.
Can I wipe the fog from my windshield?
It may seem like the fastest defogging solution would be wiping down the inside of your windshield with a towel or shirt sleeve. But try to avoid this if at all possible.
Wiping fog from the windshield may help your visibility for a few moments, but the condensation will be likely to return. When it does, the streaks you’ve made wiping the fog away will make visibility even more challenging.
Can I defog my windshield without air conditioning?
We’ve already established that using your car’s AC system when defogging can help remove humidity from the air. But what if your car doesn’t have air conditioning (or it’s not working)?
Don’t worry. You can still defog your windows by following the other steps above.
Just keep in mind that your car’s climate control system will have a harder time removing the fog for good. This means you may have to keep the heat on high or drive with the windows cracked for the duration of your drive.
How can I prevent windshield fogging?
If frequent windshield fogging is an issue for your vehicle, you may be able to reduce it by treating the inside of your windshield.
Any auto parts store will carry anti-fog products that are easy to apply. They are designed to add a protective barrier to the glass that prevents those tiny water droplets from sticking. Just take the anti-fog spray or wipes, clean the inside of your windshield and your fog problems should be greatly reduced.
In a pinch? Believe it or not, cleaning your windshield with shaving cream can produce a similar result! (Just don’t get any on your car’s exterior paint to avoid potential damage.)
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