No matter what climate you live in, this can be a constant battle. And as it turns out, a lot of drivers don’t know how to keep the temperature comfortable inside their car and battle foggy windows at the same time.
If it’s chilly out, you’re using the heater to stay warm in your car, which can result in fog on the inside of your windows.
If it’s warm and humid outside, turning on the AC (air conditioning) can cause the opposite issue ~ fog blurs your window from the outside.
The basic rule is this… you should try to adjust the temperature on the inside of the car to match the outside as closely as possible.
The reason fog develops has to do with temperature and the air’s moisture content.
On a cold day, any moisture in the air inside your car can turn into condensation. This can come from passengers breathing (exhaling), even snow on your boots.
On a hot, humid day the opposite happens. Muggy air outside your car fogs the windshield after it’s cooled by your AC system.
Either way… whether the fog is on the inside or outside, any time you can’t see clearly in all directions, it’s potentially dangerous.
So here’s what you do…
When it’s colder outside than inside your car… first, turn the heat on max. Then turn on the AC, which will pull the moisture from the air as it passes over the cooling coils. Next, turn off the recirculation button so colder, dryer air is brought into the car. Or if possible, crack your windows for a couple minutes to help exchange the humid interior air for dryer outside air.
When it’s warmer outside than in your car… first use your windshield wipers. This will help get rid of the condensation until you’ve balanced out the temperature. Next, warm up your car. Turn down the AC to the lowest (least cool) setting to increase the temperature without it becoming too uncomfortable. If this doens’t work, turn off the AC completely. Leave recirculation off.
Just remember in either situation, don’t recirculate the air in the cabin. You want fresh air to enter through the vents rather than the old, recycled air that was causing the problem. Keeping the same humid or dry air inside will just perpetuate the problem.