It’s a part of winter driving that happens all too often: You got the ice off the outside of the windshield, but inside a frosty fog clouds your vision. What’s going on, and how do you get rid of the fog so you can get on your way?
Clearing a foggy windshield up isn’t as simple as turning on the defroster. Keeping your window clear in the winter is all about balancing the warmth and moisture inside your car with the cold, dry air on the outside. Too much moisture, and your cabin will reach the “dew point,” which leads to fog on the window. Until your inside is dry, your glass will remain fogged—a dangerous proposition for you and the drivers around you. Here are five simple steps to ensure your windows stay clear.
- Make Sure Your Windshield Is Clean: Dirt on the inside of your windshield gives moisture more to cling to. Use a good glass cleaner to remove any film or dirt that may have collected on your windshield.
- Warm the Engine: Before you hit the defroster, give your car’s heating system a few minutes to warm up. The air duct temperature needs to reach about 130 degrees before the defrost mechanism becomes effective, says John Paul, AAA’s Car Doctor. But don’t turn the car on and walk back in the house. That’s how cars get stolen.
- Lower the Moisture Level: Fogging occurs when warm, moist air inside the car hits the cold air outside your windshield. Your snowy boots, wet gloves and even that cup of steaming coffee, as well as your breathing create moisture in your car. We don’t recommend holding your breath for the duration of your drive, but if your coats or gloves get wet while clearing off the car, consider putting them in the trunk before heading off.
- Blast the Defroster: Once you turn the defroster on, turn it up high. You need to cover 90 percent of the glass with air in very poor weather (i.e., freezing rain or snow and very cold temperatures), according to Paul, in order for the defroster to work effectively.
- Don’t Re-circulate: Make sure that you are taking in fresh air from the outside of the car (if it’s snowing, clear the outside vents before pulling out of the driveway) by turning the recirculate button off. If you are recirculating air, Paul says that you are simply recirculating your own breath. This means that moisture never leaves the cabin and de-fogging the windows becomes very difficult, if not impossible.
Finally, Paul says that lowering your windows to equalize temperature and dry out the cabin usually isn’t necessary, unless you have an extraordinary amount of moisture in the car. So you don’t need to freeze yourself and your passengers to see well.
If all this sounds a bit much, you might want to consider buying a car with automatic climate control. This system not only maintains a consistent temperature, but also monitors and controls moisture levels, so that windows never fog up. This feature is commonly found on new cars, but is not always standard.
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