What is the reason why the fog on the car windshield cannot be blown away?
3 Answers
The reason why the fog on the outside of the windshield cannot be blown away is the temperature difference between the inside and outside of the car. The temperature inside the cabin is higher than outside, causing water vapor inside the cabin to condense. Fogging on the front windshield can be divided into internal fogging or external fogging. Regardless of 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 when the air humidity is high, warm and humid air encounters the cold front windshield, releasing heat and liquefying, thereby creating fog. There are three solutions for fogging on the front windshield: 1. Use the external air circulation + direct airflow to the front windshield + increase temperature + increase fan speed + do not turn on AC: This can solve over 90% of windshield fogging. The advantage is that it does not additionally increase fuel consumption, but the disadvantage is that it may make people feel uncomfortable. 2. Turn on the AC: It doesn’t matter whether internal or external air circulation is used, adjust the temperature and fan speed appropriately, and the airflow direction can be random. This can solve almost all fogging issues. The advantage is that it is comfortable and simple, but the disadvantage is that it consumes more fuel. 3. Apply a windshield defogger or detergent to the inner windshield: This can prevent fogging for a period of time. The advantage is that you don’t need to use the heater to remove fog, but the disadvantage is that it requires proper application, may produce odors, and only works for a limited time, requiring repeated application.
I've driven for several years, and the issue of foggy windows that won't clear is incredibly frustrating. Most of the time, it's due to a problem with the air conditioning evaporator, such as ice blockage or a dirty filter, which prevents cold air from blowing out, causing fog to accumulate on the glass. Other times, it's because the outside humidity is too high, or the window seals have aged and are leaking air, allowing moisture to seep in and not dissipate. It's best to check the air conditioning system during seasonal changes, clean the evaporator, and replace the filter to prevent this issue. If the fog is heavy while driving, turn on the external circulation with maximum fan speed and wait patiently for a few minutes—it usually helps. Don't underestimate this problem; foggy windows obstruct visibility and can easily lead to accidents.
The car window fog won't blow away - I've researched this. The most common issue is incorrect AC settings. If the airflow is too weak or the temperature is set wrong, the fog just lingers. Also, when there's a malfunction in the AC compressor or fan system, the cooling efficiency drops, making it hard to clear the fog. Don't forget - with large temperature differences between inside and outside (like cold winter starts), you'll need to wait for the engine to warm up before hot air can defog. My advice: use recirculation mode more often during normal AC operation, as it dries the air faster to disperse fog. Simple troubleshooting: check fan speed and replace the cabin air filter.
