Why Does the Inside of the Car Windshield Frost Over?
2 Answers
The reason for frost forming on the inside of the car windshield is: after parking, the air humidity inside the car is relatively high. When the car's temperature drops, the moisture in the air inside the car condenses on the windows due to the cold. If the temperature drops to a certain level, the water droplets on the windows will freeze into ice. The windshield is an important part of the entire vehicle, designed to meet the needs of interior lighting, ventilation, and the driver's and passengers' visibility. Methods to remove frost from the inside of the car windshield include: 1. Use a hard plastic scraper to remove the ice; 2. Spray a de-icing agent on the windshield; 3. Cover the windshield with a cloth after parking; 4. After the engine's coolant temperature rises, turn on the car's heater to blow warm air on the windshield; 5. Open the doors to ventilate after parking, equalizing the temperature inside and outside the car.
I've been driving for over 20 years and have encountered frost forming on the inside of the windshield several times, which is really annoying. It usually happens in cold weather when there are many people in the car or when wet items are left inside, such as umbrellas or sweaty gear after sports. The moisture accumulates in the car and can't escape, while the outside of the glass is cold, creating a significant temperature difference that leads to frost. I remember one time after taking the kids skiing, we left wet ski clothes in the car, and the next day the windshield was completely fogged up. The solution is simple: before driving, use the heater to blow warm air or keep a dry cloth in the car to wipe it down. Prevention is even more important—avoid leaving wet items in the car, check the window seals in summer to prevent aging and drafts, and regularly inspect the sealing. If this happens frequently, insufficient refrigerant in the air conditioning system might reduce dehumidification efficiency, so it's best to visit a repair shop. Safety comes first—frost obstructs visibility and can easily lead to accidents.
