I have this strange issue in my 2007 Impala. The car windows are always fogging up like crazy. It’s so bad some mornings that I have my defroster on high and I am still peering through a 8 inch hole on my windshield. I don’t get it. I’ve tried adjusting the air intake so it is bringing in fresh air (not recirculating) and that has no effect. In fact, that setting is not changeable. When the defroster is on, it automatically stops recirculating air and you can’t change it. My side windows and back window are so fogged up, I can’t see anything out of them. I’ve tried using that defogging spray but that is a pain to have to use every morning.
Even if it’s cold, you need to turn on the a/c for its dehumidifying effect. You can turn up the heat at the same time, if you’d like. Turn off when fully defogged, then back on as needed. And yeah, always recirculate the air, you don’t want the humid air from outside coming back to fog you up.
Step One: Bring a towel, old t-shirt, SOMETHING to wipe down the windows so you can drive safely, but don’t leave the towel in the car.
It’s possible there is something in your cabin that is wet, or a leak of some sort bringing moisture into the cabin. Check the carpeting and anything stored in the cabin. Your car is old enough to have developed a leak. Be sure to check under the dash carefully as well.
If that is definitely clear, I’d drive for a while with recirculated air, A/C on, and the heat turned all the way up. It should get the cabin good and hot, evaporating the fog, while squeezing out that moisture on the A/C cycle.
Definitely check for wet carpeting. Could be a leaky door seal, sunroof, trunk, or anything. However, this also happened to me when my car’s heater core developed a leak. So it was pumping in humidity through the vents and it actually made the fog worse. There was also a sort of sweet smell from the antifreeze. Crack open the windows.
I have to take exception with voltaire’s advice. If it’s above 50ºand wet out, then the a/c is probably the best idea, just turn the temperature up until it’s comfortable. However it shouldn’t be the case that you need to recirculate as long as the a/c is working. I’ve only ever needed to recirculate on super hot days. If it’s dry outside, no matter the temperature, then the windows shouldn’t fog up with fresh air being brought into the cabin, a/c or not.
Below 50º, especially if it’s dry outside, then the a/c is totally not necessary and you also don’t want to recirculate. Recirculate with the a/c off can absolutely lead to foggy windows since the moisture from your breathing can’t dissipate. In a lot of cars the a/c won’t run if the temperature is below freezing anyway. Warming up outside air to cabin temperature, especially air below freezing, even if it’s saturated with moisture, dries it out significantly.
Fresh air is brought into most cars from an opening around the base of the windshield, where the wipers usually rest. Check to make sure snow, ice, leaves, or squirrels have not clogged this opening up. If the inlet is clogged the dashboard control that changes from fresh / recirculate has no effect, you’re always recirculating the humid air.
Also, does the inside of the car smell like coolant? You could also have a leaky heater core that’s misting the inside of the glass. Evidence of this includes the coolant smell and paper towels that get distinctly tinted green or orange or blue when used to wipe the inside of the windshield clean. No fun.
I also once had a car that fogged up like crazy on the inside. I found using Rain-X on the interior glass kept it from fogging. I see they make a product specifically for this purpose, but I just used the regular stuff.
Yep, it’s humidity. There’s a canister of stuff you can get. It’s called
‘Stay-dri’’ (or something like that). Put it in your car and leave it. If you park in a garage make sure your windows are up.
I’ve had the issue with multiple cars living in the midwest with the longest period in Michigan. The worst was my old Nissan Pickup (seriously that was the only model name it had) which was just a small truck with almost no features. It was so small a cab that it didn’t take much water to build up and cause problems.
Winter can see a lot of moisture come into the vehicle. No matter how much you try to clean off your shoes/boots before getting in snow and ice does. A preventative measure is making sure when you do hang your feet out the door and clap them together whenever there’s snow or ice.
It sounds like you’re way past prevention, though. I had poor results with water absorbing silica gels. They help but IME are overwhelmed by the amount of water a sloppy winter can bring into the car. Bringing your floor mats inside to defrost and dry can get a bunch of water out of the system pretty quick. I’d do it overnight at times when the internal frost was getting bad. If you own a hair dryer that would be quicker but I don’t keep one around. There can still be plenty of water that settles in upholstery and the carpet. My usual approach was “baking it out.” Crack a window or two and crank the heat on a longer drive or two. Don’t use recirculation; you want the maximum amount of humid air being pushed out the window as it’s replaced by dry external air. It’s even better if you can open the doors and let it air out for a minute or so when you hit your destination. A nice windy day where you can get the wind coming from the side is awesome. A couple seconds of wind through the cabin can make a world of difference if you’ve cooked most of the water out into the air first.
I’d start with the external air intact check mentioned above, though. Everything is harder if you aren’t bringing in dryer air from outside.
It doesn’t even require much moisture if it’s cold enough. What someone wouldn’t notice here can be pretty annoying in colder climates. My problem was when I lived in IL
Yes, I live in Michigan and it was 14F this morning. jjakucyk’s idea makes alot of sense. I’ve noticed that I’ll be driving down the road, suddenly buckets of humid air comes pouring out of my defroster and my windows fog up in seconds. It’s dangerous in the extreme. I’ll ask my mechanic to check the heater core.
Over how long a drive period are you talking? Is your heater blowing warm air? Is the engine temp guage up near or above 180? Do you always travel with a hot drink? Is the frost on the inside windows before you start the vehicle? My truck has that as the sunroof developed a leaky seal last summer. I used to have an S10 pickup that automatically turned the AC on when the defrost was on. Per my mechanic, it was to dry the recirculated air. If the car gets to be blowing uncomfortably warm air on the defrost, I’d start looking for the moisture source. Leaky heater core or spilled drink most likely.
Um, no, it’s the other way around. The humid air comes from the humans breathing (and sweating?) in the car. And, eventually, from the snow and ice in the carpets that melt as the heater is running. You need some amount of exchange with the outside to reduce humidity.
I’m going with those who are suggesting a leak. I have a 2005 Monte Carlo, and they are known for having a leak in the fire wall. The carpet on the passenger side was damp which was the first clue - once it got cold, the windows fogged from the inside. I was able to locate the leak (Google it), seal it, then dried the car out in the garage with a space heater. No problems since.
I had the same problem and as noted by Voltaire, my mechanic said always keep the AC unit on in the winter, (regardless of the outside temperature) and do nothing different with the interior temp settings, eg: turn it up high when you get in then dial back to comfortable after the car heats up (whatever you like) etc.
When I said “WTF! AC in the winter???”, he said the AC dehumidifies cabin air at any internal or external temperature. Contrary to a couple of comments, when this problem happens, it’s not the moisture in your breath causing the windows to fog, it’s usually all the moisture in the carpets evaporating into the air as the cabin heats up. That overwhelms the car’s defogging system.
Solved my problem immediately. I now keep my AC on all the time in the winter.
Use recirculate ONLY to get coldest A/C, or briefly if traveling through an extremely bad-smelling area. Do NOT use recirc for heat, defrost, or vent functions.
Antifreeze leak in the heater core will cause lots of fogging since the ethylene glycol does not evaporate well. The condensation should seem slightly oily if that is the case.
