How to Defog Your Car's Windshield
It's a simple as the press of a button (or two)
When it comes to riding in cars, some like it hot. I’ve tried cracking the windows in winter to defog the windshield, only to be met with howls of protest from the rest of the family. So what exactly is the best way to defog the windshield so you can see where you're going?
Allstate and Michael Calkins of the drivers training division of AAA offer these solutions.
Related: 4 Tips For Safer Winter Driving
In cold weather
If it’s warmer in your car than outside, that will typically cause moisture to condense from the air onto the car windows. The solution is not necessarily to lower the temperature inside the car, but to lower the humidity of the air, says Calkins. Turning on the AC does this, but of course you don't want to freeze to death. Here's the solution.
Press the defog or defrost button. This is the simple answer if you have a newer car with advanced climate control. The defog/defrost button "does most of the work for you — changing the air ducting to the windshield, turning on the AC, turning off the recirculate function and providing the warmest air available at the time,” says Calkins. Crack the windows/sunroof for a few minutes "because it aids in exhausting humid air from inside the car," he says.
If you have an older car, turn on the AC — and the heat. Turn on the AC, set the airflow in the defroster position, crank up the temperature (so you won't freeze) and put the blower on high. Make sure the recirculate button is turned off, otherwise, you’ll create more fog by recirculating the moist air. Also crack the window for a few minutes.
Blowing hot air at the windshield won't hurt matters and will in fact help. To get rid of the condensation (water droplets) on your windshield, you need to evaporate the
water, says Calkins. "Hot air will do this better than cold air, and dehumidified hot
on) will do it even faster. In fact, before AC became common in cars, the defroster simply
directed heated air to the windshield because that was all that was
Related: How to Drive in Snow
If you don't have AC, crack the windows for a short time. Also set the airflow in defroster position, temperature cranked up, blower on high, recirculate button off.
Shake your feet. If there is snow on the ground, AAA advises kicking the snow off your boots or shoes before entering the vehicle. Otherwise it will add moisture to the air in the car and make fogging worse.
In hot weather
In hot weather, the moisture will condense on the outside of your car windows vs. the inside. The solution? Use your windshield wipers. At the same time, turn down the AC if you can stand it. “This may help slightly by providing warmer air through the defroster,” says Calkins.
Related: Drive Safe, Arrive Alive