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Foggy car lights are not all caused by water intrusion

Car lights are the eyes of the car and are of great significance to safe driving. However, with the advent of cold weather in winter, the phenomenon of car headlights fogging up is gradually increasing in various places, and it may even condense into many water droplets, causing many hidden dangers to driving safety and making people worried.

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However, is fogging in car headlights a quality problem? What is the reason? Is there a difference between foggy headlights and water in the headlights? What should you do if your car's headlights become foggy? Next, we will do a detailed analysis for you.

What are the dangers of foggy headlights?

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In weather conditions with a large temperature difference between day and night or high humidity, it is very annoying if fog appears in the headlights. It not only affects the light transmittance of the car headlights, but also makes the lighting effect dim and dim, and may even be very It is difficult to see the road conditions clearly and there is no way to send out correct warning signals, which poses a huge hidden danger to driving safety.

In addition, fogging of the headlights can easily cause the headlights to form astigmatism, which cannot correctly form a proper focus, causing dazzling light pollution to vehicles in the opposite direction; what is worse, it can also easily cause corrosion to the relevant electrical components of the lamp set. Serious consequences will damage the optical effect of the lamp unit and affect the service life of related parts in the long run.

The true mechanism of headlight fogging

The luminous sources of car headlights (halogen bulbs, xenon bulbs, LED light sets, laser light sets) all emit huge amounts of heat, causing the air inside the headlight shades to expand and contract, creating huge air pressure. Therefore, many cars The electrical engineer will add a "breathable" rubber vent pipe or vent to the headlight assembly to avoid problems caused by excessive pressure in the lamp.

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During the rainy season, heavy rain or winter, when the headlights go out and the temperature inside the lamp unit drops, water molecules in the air are easily sucked into the cavity of the lamp unit through the rubber vent pipe or vent hole.

When the temperature inside the headlight cavity is unbalanced and the temperature difference between the inside and outside of the lampshade is too large, water molecules in the humid air will gather from high-temperature places to low-temperature places, increasing the humidity in these parts, and then condensation on the surface of the inner lampshade. , and usually concentrated in the lower half.

However, headlight fogging is not a serious quality problem. It is caused by many special reasons. However, within the warranty period, you can generally find a 4S store to help solve it.

These reasons make your car headlights more susceptible to damage

Due to the structural design of automobile headlights, the temperature near the bulb is the highest and the temperature away from the bulb is the lowest. Due to the different structural design of the automobile headlight cavity, the temperature field, flow field, and material selection are different, and the probability of fogging is also different.

The more regular the inside of the headlight is, the larger the gaps between the components, the better the air circulation, and the less likely it is to fog up. The opposite is true in narrow areas, where airflow cannot circulate and fogging is more likely to occur in these areas.

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From a physical point of view, there is a condensation core inside the headlight. When dust and other particles enter the headlight cavity, light distribution mirror or the inner surface of the lampshade, it is because the surface is not smooth, thus creating conditions for air water molecules to find the condensation core.

In addition, the airtightness of the headlight assembly has deteriorated. When modifying the vehicle's headlights, if an inexperienced technician disassembles and closes the headlights, moist water molecules can easily enter the lamp cavity.

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The most common thing is that the engine cooling system is also one of the reasons that affects whether the headlights will fog up when the vehicle is wading in water or after a heavy rain. Because in a closed engine compartment, water is evaporated by the high-temperature engine compartment into a large amount of water vapor, which easily penetrates into the interior of the car's headlight unit through the vent pipe or vent hole.

The same goes for washing a car too violently and using a high-pressure water gun to flush the engine compartment, which will increase the chance of water molecules entering the lamp cavity.

What is the difference between headlight fogging and water damage?

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If water enters the headlights of a car, it will not look like white mist from the outside, but larger water droplets will appear on the headlight shades, and obvious water accumulation will be seen in the lower part of the lamp cavity.

This situation is mainly due to problems with the sealing of the headlight assembly, or directly to damage, penetration, or rupture of the outer casing. Unlike foggy headlights, which can be easily eliminated on their own, water damage to car headlights is a serious maintenance problem that is generally difficult to repair. The headlight assembly needs to be replaced to completely solve the problem.

How to correctly deal with foggy car headlights?

For manufacturers, designing a better headlight structure, rationally setting the ventilation holes and design positions, and strengthening the airtightness of the lamp units are the keys to reducing fogging of car headlights.

Of course, the application of defogging coating technology is also a key technology to solve the problem of headlight fogging. Anti-fogging coatings are very hydrophilic and have large water surface tension, which can prevent water droplets from forming on the surface of the coating. Apply it on the surface of the coating. Inside the lamp cavity, fogging can be avoided. However, due to the high cost, many OEMs will not take the initiative to adopt this approach.

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Riders, don’t be impatient when your headlights become foggy. Be sure to use a baking lamp to bake the headlights directly. Generally, the headlight covers are made of resin or plastic material, which can easily be baked or even burned by a large amount of heat. Cracked, ultimately the gain outweighs the loss.

Generally speaking, the best way to deal with it is to check the tightness of the headlight assembly, and then turn on the headlights after confirming that they are correct. After about fifteen minutes, use the large amount of heat emitted by the headlight bulbs to evaporate the fog.

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If it is judged that the car is not only foggy, but also has water accumulation, then you need to rush to the 4S store or maintenance service agency in time to disassemble the headlights to clean the water accumulation, and check the condition of the headlight assembly. If necessary Re-seal or replace the entire assembly.


Fogging of car lights is affected by many factors. To solve the problem of fogging of headlights, in addition to manufacturers providing better quality headlights "from the source", all car owners should also develop the habit of regularly checking the headlights. Get used to it, check whether the headlight lampshade is damaged or cracked, grasp the fogging situation of the headlights in a timely manner, and make reasonable treatment methods to keep your car with a pair of bright eyes!

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As one of the leading enterprises in field, CARCUU has been focusing on producing high-quality products including .We have been paying attention to producing finest and providing the most professional service.Foggy car lights are not all caused by water intrusion is a quality-reliable product with good sealing performance. It is widely used in machine tools, boats and ships, autos, aerospace equipment, agricultural machinery, metallurgical machinery, petroleum machinery, chemical machinery, and construction machinery.

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