Reasons for Fogging in Car Headlights on Rainy Days
2 Answers
Fogging in headlights is normal. This is because there is a ventilation and heat dissipation rubber tube at the rear cover position of the headlight structure. It is also due to this rubber tube that moisture from the air enters the headlight and adheres to the lens, creating fog. In severe cases, water droplets may form. This situation is most likely to occur during winter and rainy seasons. Below is relevant information: 1. Mild Fogging: First, mild fogging occurs, and the reason for this type of fogging is only related to the humidity of the air. Generally, the amount of water vapor condensed in the headlight due to fogging is not much. The headlight assembly has several intake and exhaust holes, whose function is to balance the air temperature inside the headlight when it is turned on, allowing hot air to be expelled and cold air to be drawn in. 2. Severe Fogging: Severe fogging is usually caused by cracks in the headlight assembly, improperly fitted dust covers, holes in dust covers, aging sealing glue, etc. After driving, the temperature inside the headlight is still very high, and a large amount of highly humid air enters. If the outdoor temperature is relatively low, a layer of fog will condense inside the headlight assembly.
As an experienced auto mechanic, I've encountered countless cases of headlight fogging after rain. The most common cause is aging or damaged lamp housing seals, allowing rainwater and moisture to seep inside, which then condenses into fog when there's a significant temperature difference between inside and outside. Some vehicles are designed with ventilation ports to regulate air pressure, but these can easily get clogged and accumulate moisture during rainy weather. Additionally, high-pressure water impact during car washes may accelerate seal deterioration. I recommend car owners first inspect the headlight housing for any cracks, then observe how quickly the fog dissipates when turning on the lights after rain. If the fog persists, promptly replace the seal or the entire lamp housing - the cost is only a few hundred yuan. Don't delay repairs, as moisture corrosion of electrical circuits could lead to much more expensive fixes. Developing regular maintenance habits by keeping the lighting area dry can prevent major issues.
