How should I set the controls for the heater/defogger/defroster in my car to keep my windows clear in cold and/or rainy weather?
Ask a rocket scientist.:rolleyes:
The key thing is not to turn on the defroster until the engine warms up. Otherwise you’ll just be sending moist air from above the engine onto the cold glass, making it fog inside. Start off with the windows open a crack, so your breath will be drawn out and won’t condense on the windows.
I can never figure it out either. I think it depends on which side of the window the fogging occurs. Anyway, I just try cold first and if that doesn’t work, then I try hot, and if that doesn’t work, I try to make it even with the outside temperature (somewhere in the middle).
The winter, usually hot works.
For what it’s worth.
When I was growing up in Fargo, ND. I always found that having the window cracked seemed to help with the defrosting. It was like releasing a vacuum in the car thereby letting more air reach the windows.
There shouldn't be to much moisture in the defroster either way from what I understand because of the air-conditioner.
I always turned it on hot and let it run.We did this thread a while back:
http://boards.straightdope.com/sdmb/showthread.php?threadid=41740
The quick answer is: make sure the air conditioner is on. It might come on automatically when you turn on the defroster/defogger, or you might have to press a separate AC button. Consult your vehicle owner’s manual.
Well I’ll be damned. So my girlfriend was playing games with me. She always turned on the A/C to defrost the window, and only played with the temperature to fool me.
I guess I’m living proof that not all men know about cars.
There is another alternative. My previous car was a Jetta that always got fogged up. After trying all the permuations of opening/closing windows and various defroster settings, I happened to stumble upon a defogging liquid that you apply inside the window(s). Works like a charm, one application lasts for months. I cant remember its name but it comes in a black plastic bottle, and probably, I got it at K-Mart (or Big K? Whats with that?).
Rain-X Anti-Fog. They also make an exterior coating which helps keep rain & mist from sticking. That comes in a yellow bottle.
Rain-X Anti-Fog is better than turning on the A/C when its 20 outside. There might some stuff that is like Rain-X Anti-Fog, make candle wax?
Adjusting the temperature when the AC is on is not necessarily playing games. I turn the AC on and the defogger on with a high temperature to quickly defog the windows when the condensation is on the outside. The AC dries the air out and the heat holds more moisture. I find that works best when the condensation is on the outside of the window, but I don’t know why.
Did you guys even read the question? The OP is about fogging in COLD weather, not warm weather. Turning on the AC isn’t going to eliminate fogging in cold weather, which primarily comes from condensation of humid breath on the cold glass.
There are only two ways to eliminate condensation (fogging).
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Eliminate the source of the excess moisture. You can do this by either stopping breathing, or by opening up the air vents or windows to carry away the humid air. If it is exceptionally humid (i.e. raining and cold) this may be impossible.
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Raise the temperature of the air and the windshield above the dew point. This means turning on your defroster and the heat.
I have a Camry, which is the best car I ever owned, but has a really crappy ventilation system and is constantly fogging up in winter unless you have the settings just right. If I have the vents closed and set to recirculate the interior air, the car will fog up in even slightly cool weather. If I get more than 3 people in the car and the vents are closed, the car will fog up in just about ANY weather. I’ve tested all the various theories (including the AC theory) and I assure you, you have to turn on the heated defroster. There are no tricks to work around the laws of physics. I mean, really, if AC could defrost your windows, auto manufacturers would have the defroster hooked up to the AC instead of the heat.
Dude, one of the A/C’s main parts is a dryer, which removes moisture from the air. And it works just as well with cold air as it does with hot.
Using your A/C, on the Defrost vent setting, and recirculating the air, is the best way to defog your windows.
–Tim
I’m with Homer on this one. That’s what I do-- put on the A/C, turn the temp all the way to the hot side, and divert the air to the windshield vents. A/C does not necessarily mean “cold air.” It dries the air. I run mine frequently in cold, rainy weather.
When I turn the defrost on in my car it actually automatically turns the A/C on for just this reason. The heat is on not the cold air. The A/C setting turns on to remove moisture from the air while the heat from the defrost blows hot air on the windows. I have to think the car was manufactured to turn the defrost and the A/C on at the same time for a reason and it seems to work.
Jawofech
I just open the window. No more fog.