I went out to my car one morning and the windows were all fogged up with condensation on the inside. They have been doing that for quite some time, but I would usually just grab a towel and wipe them down. Well, I finally decided to do something about it.
Why Do Car Windows Fog Up?
The reason is simple. Condensation builds when warm, humid air meets a cool surface. Sometimes if you’re in a warm, humid environment and have the air conditioning on really high, moisture can collect on the outside of the windshield.
Here are some of the most common causes of interior car moisture:
• Wet clothes or boots
• Human breath
• Damp carpet
• Leaks from the sunroof, vent system, doors, or windows (check to see if any areas of the carpet or trunk are wet)
• Hot, steamy food or beverages
• Coolant leaks into the vehicle from a heater core
So, first things first. You need to find and repair the source. If there is moisture on the windows and you aren’t driving around with three or four friends chatting it up, you may have a leak or you may just have some really wet floor mats as a result of tracking in puddles from the latest downpour.
If it is a leak, it may be from a bad door or sunroof seal, or a clogged A/C drain. You will want to locate the wettest part of the car and start looking in that area. No matter the climate, you will eventually see deterioration of door and sunroof seals where they will become worn and torn from age. One preventative trick for that is vaseline on the rubber seals. It acts as a conditioner for the material and will help create a better seal. Of course, once it is cracked and torn you will need to replace it.
If you find the leak is under the dash on the passenger side, check your A/C drain. It could be clogged with pine needles and leaves.
My vehicle is a fourth generation VW and they are known to have sunroof drain problems. I replaced the roof drain hoses years ago, so I know that is not my source, but something else to keep in mind when searching.
The problem I was having was with the rain tray. It’s a plastic cowl that catches water as it drips down the windshield and directs it to either side of the car to drain off. Well the plastic didn’t want to stay put in the groove on the bottom of the windshield. It would pop up over time and allow the water to run right down into the fresh air intake vent and in turn, drip onto the floor.
I chose to use a windshield sealing gel to fix the problem. I wanted something waterproof to hold that plastic piece down, but nothing permanent. After all, that piece of plastic will inevitably be removed at some point and I would rather not break it. Just a tiny bit was used. A few small drops in the groove where the cowl snaps in and then once it set, the leak was fixed.
The Leak Is Fixed
Okay, so no more water is coming in, but we’re not done. That carpet is soaking wet from the last downpour and we need to clean that up. If there is a puddle, you may want to attack it with a wet/dry vacuum. If you don’t have one, then lots and lots of rags. Soak the water, ring the rag out and repeat. Remove as much of that water as you can. If possible, leave the windows open on a sunny day to help dry it out.
Now the puddles are gone and the leak is fixed, but there is still moisture left in the carpet and probably in the trunk. There are a number of items on the market that will help you at this point in the process. Usually made with a silicon based product, they will absorb the moisture in the air. One option is to use the little containers that are made for keeping humidity down in a closet. There are a number of other options and any of them should do the job. If you find that the container is filled with water and the humidity is still there, simply use another one. It may take a few containers and will probably not work over night, but it will do the trick if the source is fixed.
Another great trick is to use cat litter. Some people just toss an open bag of it in their trunk for a week. You shouldn’t need that much, a cereal bowl or two should be sufficient (depending on the severity of the problem). If you are concerned about it spilling, put a thin rag or cheese cloth over the top and secure it with a rubber band. Leave it in the car for a week and you should see the moisture dissipate and eventually disappear.
If not, revisit your search for fixing the source. You may have more than one leak.
Tips To A Moisture-Free Car
1. Look for signs of damp — Since condensation is caused when warm air in the car comes into contact with the cold glass of your windshield, it’s important to remove as many sources of moisture as possible. While it might sound obvious, anything in the car that is damp will give off moisture which will turn into steam and then into fog. Check for leaks—especially in the trunk. Lift up the rear carpet and make sure the rear wheel well isn’t damp or full of water.
2. Leave a couple of windows slightly open on warm or sunny days — Leaving a window slightly ajar during warm winter days will allow the sun to warm the vehicle’s interior and circulate the moisture out of your car. Just be sure to shut the windows before nightfall to avoid getting a car full of dew.
3. Close your windows on wet days — This one also probably seems obvious, but we’ve all forgotten to close a window or sunroof properly at least once and paid the penalty for it. Keeping moisture out of your car is the first step to keeping fog off your windshield!
4. Use your air conditioning — But it’s winter! Who needs AC in the winter? Well actually, you do. Air conditioning removes moisture from the air, so turn it on when your car is at a comfortable temperature. That aside, you should use your air conditioning at least once a month during the winter to keep the system ticking and stop any pipes from drying out and leaking gas. It also stops it from smelling when you do turn it back on again in the summer.
5.Turn off your re-circulation (recirc) valve — All cars have re-circulation valves, especially cars with air conditioning, but a lot of people haven’t got a clue as to what it is. It’s usually shown as a picture of a person being smacked in the face by a huge arrow (or sometimes a “C” shape with an arrow at the end). What it means is that instead of getting new air from outside, the system is recycling the same air from your car through the system. You won’t get rid of fog with the re-circulation valve! Make sure you turn it off so you can get new, dry air from outside.
6. Try an anti-fogging product — If the fogging still doesn’t go away after trying all these steps you could try an anti-fogging product like Rain X Anti Fog Repellent. It can put a slightly visible film on the window and doesn’t last very long in my experience, but does help to dry a windscreen quicker. It needs regular application.
7. Try a Moisture Magnet – designed to attract moisture, the Moisture Magnet can be useful for vehicles which a small amount of damp or condensation. Reviews are mixed but I have a friend who was very pleased with the results.
8. Remove wet clothing from the vehicle — This one also sounds obvious, but wet clothes will lead to more moisture in the air.
9. Dry wet seats — If a seat gets wet either from clothing, a wet umbrella, or a spill, use your car heaters or a hair dryer and dry them right away with the windows open to let the moisture out.
10. Remove trash on regular occasions — Leaking bottles, moisture left in cans, and rotting apple cores all create moisture which can and will end up on your windshield.
11. Air the vehicle as often as possible — Put the heaters on full and open the windows when driving if you can. Direct the air vents on the carpets and seats when possible.
12. Use your garage — The ambient temperature in the garage will be higher, which will prevent dampness. You can also leave the windows open to help air out the car if the garage is secure.
13. Check for a leaking heater core – a heater core is basically a small radiator placed inside the vehicle (usually under the dash) which has warm coolant from the engine running through it. When you switch on the fan air is blown through the fan and made hot by the warmth of the hot radiator. If this leaks, coolant soaks into the carpet.
14. Avoid car covers — Some car covers claim to be breathable but I’m not convinced; however, for a car with a severe leak they will obviously offer some extra protection. Just exercise caution.