A windshield that is frozen on the outside is a normal phenomenon that every driver is ready for. Another thing is if the ice appears from the inside. Why the windshield freezes from the inside, and how it is dangerous – let’s understand. There are several explanations for why the glass from the inside is covered with ice.
Increased humidity

Ice forms on the glass due to condensation forming in the cabin. Or, to put it simply, due to increased humidity. If the dampness appeared in the cabin – a consequence of melting snow, which was brought in on the shoes, it is enough to remove the puddles, wipe the mats dry, and you can forget about the problem.
Seals

If the rubber bands on the doors are worn or torn, they are unable to protect the interior from the penetration of cold street air. As it cools, it falls into the dew, and overnight it turns into ice on the glass.
Therefore, if there are no puddles on the mats, and the windshield is freezing, it would not hurt to check the condition of the seals. If they have ceased to adjoin tightly to doorways, the problem of icing is solved simply – by replacing rubbers. Well and at the same time it will not hurt to check doors adjustment.
Interior filter

When it is dry under feet and mats all the time, and in the morning the windshield continues to remain icy, it means that there is a constant moisture inside the cabin. The simplest explanation for the problem that can come to mind is a clogged ventilation system. The cause is most likely if you haven’t changed the cabin filter in a while.
In this case, not only does it fail to cope with normal ventilation, but it is not even able to remove human fumes from the cabin. What to say about moisture from wet clothes and shoes.
Therefore, the first thing to do is to check the filter. If it’s still in more or less serviceable condition, you can clean it. But it is better to replace it. Then you will for a long time forget about ice on your windshield in the morning.
Windshield

Often icing happens due to fault of windshield itself – that is, because of loose fit of gasket. A small hole or a crack is enough for air to freely penetrate into interior. And it means that because of constant dampness the upholstery and covers will be damp all the time. And this will lead to more serious consequences.
Front windshield icing is half the trouble. It is worse, if frequent leaks and dampness will provoke car body corrosion.
Only replacement of a windshield will help to prevent such a scenario. Or reinstallation of the old one, but with obligatory replacement of seals. Certainly, you will have to pay for it, but there is nothing you can do.
Cooling system

If you have far from a new car, the windshield icing may occur because of problems in the cooling system. The matter is that the pipelines carrying the antifreeze from the engine to the heater wear out with time. If cracks appeared on them, the liquid will leak inside the car and then evaporate. Constant humidity in the cabin will provoke icing of the glass.
But it is not the most terrible thing. The main danger is that the corrosion of the car body will begin. Therefore, if you have a car “in age”, it will not hurt to check cooling system.
Ways to combat ice

What to do if you found ice on the glass in the morning? You can quickly scrape it off without waiting for it to thaw itself. But then the ice crumbs will fall on the panel, melt and turn into steam. And this means that it will be humid in the cabin, and you will again see ice on the glass in the morning.
The second option to combat condensation is to turn on the heater and as the ice melts, remove it with a dry rag. But you will not get rid of water completely, some part will still remain in the air.
The most effective is to remove the source of problem from a salon. For this purpose you should switch on air conditioner or a heater, directing a hot jet to the window. As it thaws, wipe the areas with a dry cloth. Then check if there is no water on the mats. If there is, drain and wipe them on all sides. Next, inspect the entire interior and do the same. In the final step, leave the doors open to air the car properly.
Preventive Measures
If there is nothing wrong with the car and no repairs are required, all that remains is to take care of how to prevent frost from forming.

- Before parking the car overnight, it is necessary to cool the interior so that the temperature inside and outside are the same. This can be done by opening all the doors for 10 to 15 minutes, creating a draft. If this is not possible, then 5-10 minutes before you stop, you can turn off the heater, open a window and drive in the cooling interior.
- For the night cover the window with a blanket or cloak lined with soft, fluffy material. This will slow down the cooling and remove the temperature drop, so the windshield will not freeze.
- Wipe the inside of the windshield with vinegar water or a special anti-fogging agent.
- Replace the mats and/or covers with products made of a material that does not absorb moisture.
- Put an athermal film on the windshield. This protects against freezing and prevents frost from forming.