
Press the defogging button, which has an icon of three upward-curved arrows inside a square, located at the lower right corner of the center console. Turn on the air conditioning (A/C) to the coldest setting and activate the external air circulation to defog the windows. Both cold and warm air can be used to defog car windows, but warm air is slower than cold air. The most effective method is to use cold air, which blows dry, cold air directly onto the glass, preventing water vapor from condensing on the surface and achieving defogging. The warm air method works similarly, but note that it should not be used on rainy days as it may initially worsen the fogging. Always use external air circulation when defogging car windows. The reason car windows fog up: There is a temperature difference between the inside and outside of the car. If the temperatures differ, the side with the lower temperature will have a lower saturated vapor pressure, causing water vapor to condense on the glass surface in tiny droplets, forming fog. Methods to defog car windows: Air Conditioning (Cooling Mode): Use the air conditioning's dehumidification function to reduce air humidity and remove fog. In summer, especially when multiple people enter the car without turning on the AC, the exhaled humid air can quickly fog up the windshield. Turning on the AC to blow cold air onto the windshield can help dehumidify and clear the fog quickly. If humidity is too high and the AC alone is ineffective, slightly opening the windows can rapidly reduce cabin humidity. Combining both methods yields faster results. Air Conditioning (Heating Mode): Use warm air to reduce the temperature difference and prevent fogging. In winter, blowing warm air onto the windshield raises its temperature, minimizing the temperature difference between the inside and outside surfaces and preventing heavy fogging. However, the rear and side windows warm up more slowly, requiring more time to fully defog. Whether using automatic or manual AC, turning it on aids dehumidification. Avoid setting the temperature to the coldest to prevent external windshield fogging over time. Applying Anti-Fog Products: Spray a small amount of defogging agent onto the car windows and wipe it clean to remove dirt and stains. This leaves a transparent protective film that effectively prevents water vapor from condensing into fog, especially useful in cold winters. Alternatives like dish soap, soapy water, glycerin, alcohol, or saline can also be applied. After drying, wipe off excess residue with a chamois or soft cloth to keep windows fog-free for several days.

I have a lot of experience with the issue of car windows fogging up when exiting an underground garage. Since the temperature underground is much lower than outside and the humidity is high, the warm air outside causes condensation on the windows. I usually press the defog button on the AC immediately and let the cold air blow, which clears it up in two to three minutes. If there are children in the car, I first find a safe place to stop, crack the window slightly for ventilation. Regularly, I also check the AC system to ensure it's not clogged with dust, and replace the filter when needed—this helps defog faster. Additionally, using a specialized anti-fog spray to clean the windows works quite well, but avoid wiping with plain water as it smears more. Visibility is the most important thing while driving, so developing this habit is essential for safety.

Here's how I always deal with foggy windows when leaving the garage: Immediately turn on the AC in cold air mode, set to maximum fan speed plus recirculation, and press the defog button for a quick solution. It's simple and efficient. As a tech enthusiast, I understand the principle is due to temperature difference plus humidity causing condensation, and the car's smart system can quickly adjust the temperature difference. Daily, I use anti-fog car film to reduce the problem. If the car is old and lacks this feature, opening windows for ventilation also works, but it's less efficient. For prevention, keeping the car interior dry and avoiding placing wet items can prevent fogging. In hot weather, setting the AC slightly higher helps avoid large temperature differences.

As soon as I drive out of the underground garage, the windows fog up. I have to quickly turn on the air conditioning with cold air, directly pressing the defog button. Sometimes, simply opening the window a bit to let in some air also works. Usually, when driving, pay attention to the large temperature difference between inside and outside the garage, which easily causes this. So, before leaving the garage, wait a bit to let the car adapt to the temperature change before driving. Don't clean the windows with your hands, as it can leave marks. Develop this small habit, and you won't have to worry about fogging.


