Why the windows on the inside of the car mist up, and how to deal with it

During the winter, car windows tend to fog up from the inside. This is a very unpleasant problem. First of all, it interferes with the review when driving a car. In addition, the driver is forced to be distracted by wiping the windows, which is not safe while driving. Secondly, it causes questions from the traffic inspectors, as they tend to think, first of all, that the glasses are fogged up due to the fact, that the driver took a large amount of alcohol the day before.

Condensation on car windows

Condensation is the tiny particles of water, settling in the coldest parts of the salon, which are the windows. It forms on the windows not only in old cars, but also in new ones, and the presence of super-modern climate control systems is not an obstacle to this process. What causes it and how to cope with the problem?

It is a stable myth that window steaming from inside is caused by active drinking of strong alcoholic drinks. It is on glasses the inspectors of traffic police look first of all in attempts to catch the infringer of sober way of life in a stream of cars.

The person having drunk alcohol increases body temperature and breathing becomes more frequent. The last factor may influence formation of increased quantity of moisture in a saloon. But! All people in the car, including not only the driver, but also the four passengers, must breathe intensively for a long time to make the windows fog strongly. Otherwise, the windows will not fog up as it happens with frost.

So, fogging is not caused by alcohol vapors. It is the condensation resulting from the temperature difference.

Causes of window misting

Misting of windows may be caused by:

  • improper operation of the heater;
  • air recirculation mode violation;
  • ingress of moisture into the cabin in rainy weather;
  • clogging of the cabin ventilation filter;
  • other factors.

Excessive moisture in the cabin is also dangerous, because metal parts may rust because of it. In addition, it leads to the appearance of mold, which is accompanied by an unpleasant odor. But it is possible to struggle with these problems quite successfully.

How to fight window misting?

If the windows in your car mist up in warm, but rainy or foggy weather, due to the fact that moisture has seeped into the cabin, turn on the air conditioner or heater on blowing. Using these devices will help dehumidify the air inside the car.

In cold weather, the windows in the car sweat for other reasons. Here the air conditioner will not be effective, and turning it on in the cold is quite a controversial decision. After starting the motor, a stream of cold air is directed to the windows, and since the glass is even colder, the moisture condenses on it. Wiping the windows has no effect: frost patterns reappear.

If condensation on the windows appears in the warmed up car, it can be connected with clogging of the filter of ventilation system. Because of this, the air flow becomes less intense, and the windows receive less heat. As they stop warming up effectively, they become the perfect environment for condensation to build up.

Occasionally, a malfunction in the climate control unit causes the windows to mist up. Because of this, the temperature of air flows is not regulated correctly. It happens quite often. This problem is typical for Land Rover, Kia and Chinese car brands. Sometimes, not windshield fogs, but a window in the driver’s side door. It is also connected with malfunction of the climate control unit.

In the cold season, drivers are forced to constantly turn on the heater. At the top of the hood, next to the plastic protection, there is a heater opening, which draws in air. Snow also gets in there. The warm engine causes it to melt – accordingly, moisture enters the interior, causing condensation on the windows.

In addition, the windshield sometimes fogs up because the drains of the air inlet box get clogged. They are located under wiper blades’ leads and provide air intake to heater. If the drainage is not working, there are problems not only with windshield fogging, but also with wiper mechanism.

If your car has air conditioner, check if the condensate drain tube from the evaporator is not clogged. This, too, can cause high levels of humidity in the cabin.

If there is window misting in combination with unpleasant chemical smell inside your car, antifreeze is most likely flowing out of heater’s radiator. Its vapors are very dangerous to human health. Accordingly, technical faults in the ventilation filter, climate control unit, cabin heater, etc. must be diagnosed and repaired quickly.

When a car is overtaken by a truck or an old diesel SUV, the driver usually turns on the air recirculation mode to get rid of the unpleasant smelling plume. But if you forget to turn off this mode, the air will not be able to escape unhindered from the interior to the outside, which is necessary for airing and, therefore, to reduce the amount of moisture that leads to the formation of condensation.

Check how tight the seals on the doors, windows, trunk lid and sunroof are. If moisture is seeping through the gaps, it will be very difficult to get rid of window fogging.
If you drive too fast in freezing temperatures, the windows will be intensely cooled by the oncoming air flow, and this will cause them to fog up. To avoid problems with poor visibility, just slow down.

Caring for your car interior

If all systems are working properly, you should take regular care of your car interior and follow some simple rules.

In winter, to reduce condensation factors, it may be advisable to regularly dry the cabin mats, which absorb water from thawed snow from shoes. If the mats are made of dense rubber or plastic, they do not absorb moisture, but the melted snow accumulates in them as puddles.

When hot air flows into the feet, moisture is actively evaporating and settling on the cold windshields. Sweeping or tapping your shoes against the snow before you get in the car will reduce the moisture level inside – consequently, the windows will fog less.

Before you leave your car in the parking lot, make it a rule to air out the interior. It is especially relevant if you transported passengers with wet clothes and shoes. It will reduce fogging of windows at the next trip.

You can also practice driving with ajar windows on the last part of the road before parking. In this case warm humid air will leave the salon, which will lead to equalization of temperatures on the inside and outside of windows. But in severe frosts, it is not only uncomfortable to drive with open windows, but also it is possible to catch a cold.

On the inner side of glass, over time, there appears a little-noticeable mud film, which actively attracts moisture. Do not allow its formation, regularly wipe the windows from the inside, even when they do not show the characteristic “frost patterns”. But in winter it must be done in fully warmed up interior and with the help of special means of auto-chemistry.

You may make an anti-fogger yourself: mix 20 parts of alcohol and 1 part of glycerin, and pour the liquid into a bottle with a sprayer for more convenient use.

Use clean, dry cloths to wipe windows. Do not use paper towels or wipes since they will leave streaks.

Treat your windows with moisture-repellent products in the form of sprays or aerosols. They come in two versions: the former form a transparent film on the glass that prevents moisture condensation, while the latter repels water. Apply them to dry, clean glass. Consequently, this should be done before the trip, not during it.

True, the action of these funds lasts for a short time, but during this time, the glass will not freeze or fog. It is especially important for short trips in cold or rainy weather.

Shake the snow off the hood grille, so that when the heater is turned on, the moisture from it will not penetrate into the interior. Periodically dry and ventilate the cabin with the recirculation mode, just remember to turn it off after the procedure. Avoid ice formation on the windows.

In winter, fill the windshield washer tank with non-freezing liquid, which contains alcohol. This prevents your windows from icing up. True, in this case, you cannot avoid the characteristic smell, which may be noticed by a traffic inspector.

Always warm up your car before driving. But the windows must be heated gradually, so as not to have sharp temperature drops. It is better to switch on the air intake from the street, directing the deflectors to the fogged up areas simultaneously with the work of the heater. The circulation lever must be in extreme left position. You may use electric hairdryer with heater to help cabin heater – it quickly dries air.

Keep an eye on cleanliness and serviceability of air conditioner, heater, air filters. It is possible to modernize air lines of trunk: cut little holes in the side trimming of boot compartment, install plastic grates in the appeared “windows”. It will essentially increase air outflow, improve ventilation and decrease fogging of windows.

It is important to understand, that all listed procedures will help to cope with weeping only partially, as condensate formation in warm interior is a natural phenomenon for cold, damp weather. Still, they can reduce the danger that can be caused by impaired visibility due to severe fogging of the windows.

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