What is the reason why the fog on the car windshield cannot be blown away?
4 Answers
Window windshield fog cannot be blown away due to the large temperature difference between the inside and outside of the car. The following is an introduction to the relevant content: 1. Classification: Fogging on the front windshield can be divided into internal fogging or external fogging. Whether it is internal or external fogging, the main reason is that the surface temperature of the glass is lower than the air temperature, and the air humidity is relatively high. When warm and humid air encounters the cold front windshield, it releases heat and liquefies, thereby producing fog. 2. Shortest time: Hot air defogging reduces the temperature difference on both sides of the glass in the shortest time to achieve the purpose of defogging.
I've been driving to and from work for several years, and foggy windows that won't clear up is a pretty common issue, mainly due to incorrect air conditioning settings. You need to set the airflow to windshield mode, otherwise the air will just blow elsewhere; the fan speed being too low is also no good—too stingy. A clogged filter is the most annoying—before I last changed my filter, barely any air came out, the fog just stuck around, and I couldn't see a thing while driving, almost causing an accident. Also, in the summer when you turn on the AC, if you don’t activate the AC cooling, hot air plus high humidity makes the fog even more stubborn—it’s best to check if the compressor is working properly. For prevention, I suggest clearing any residue off the glass before each drive and avoiding spraying perfume on the interior, as the oil buildup can make the fog harder to disperse. Regularly cleaning the filter and using the external air circulation to reduce humidity differences can significantly cut down on these annoyances—safety first, after all!
The windshield defogging failure is probably caused by accumulated minor issues in the air conditioning system. For instance, if the fan speed is set too low, the insufficient airflow can't disperse the fog; a clogged filter restricts air circulation, significantly reducing the AC's efficiency. Improper temperature settings are another pitfall—during winter, if the hot air isn't directed at the glass or mixed improperly with cold air, the fog lingers. On long trips, I've noticed that when external temperatures drop suddenly and the interior heating can't keep up, the fog forms and won't clear, seriously affecting nighttime driving. So, make it a habit to test the defogger button before driving, keep the fan at medium to high speed, and check/replace the filter every six months. Don't overlook these small details—safety comes first!
Foggy windows that can't be cleared pose a serious hazard, especially during rainy or winter driving, as impaired visibility can easily lead to accidents. The issue typically stems from air conditioning settings, such as not activating the defogging mode, insufficient airflow, or a faulty fan that fails to blow enough air to dry the glass. High interior humidity combined with cold exterior air accelerates fog formation, while a clogged filter further weakens airflow. When dealing with this, I immediately pull over to check the AC settings, ensuring the AC cooling is on and adjusting the air direction. If that doesn’t work, I manually wipe the windows or briefly open them to balance the temperature. Regular maintenance of the AC system can prevent this risk.
