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What are the causes of headlight fogging and water intrusion, and how to solve them?

Introduction | "Eyes" that don't shed tears are the most beautiful

Nowadays, everyone has higher and higher requirements for the reliability of cars. As the eyes, if the headlights are in tears every day, it will not only reduce safety but also destroy the appearance.

Generally speaking, we think that car lights are sealed, but in fact they are mostly semi-closed structures (there is a vent pipe on the back cover of the headlights). Its advantage is that the lamp body has ventilation holes, and the headlight cavity is breathable to the outside world. This allows the pressure of the lamp to be balanced in the two states of lighting and extinguishing, maintaining the normal operation and stability of the headlight. However, the disadvantage is that water Parts may enter the cavity during the ventilation cycle.

What are the causes of headlight fogging and water intrusion, and how to solve them? 1

▲Traditional halogen bulbs or xenon lamps will generate a lot of heat after being lit. Without ventilation holes, the air inside the lamp will expand due to heat and may burst.

The number of complaints about fogging and water intrusion of car lights has always been high. Especially in autumn and winter, rains are frequent and temperature changes are large, which are more likely to cause such problems. Today we will talk about the causes of fogging and water intrusion in car lights, and the solutions.

1. Causes of fogging and water intrusion in car lights

We know how water comes in, but to be precise, fogging and water intrusion are two different phenomena.

After the fog inside the car lights appears, it takes 1~1.5h to completely eliminate the fog when the lights are turned on; in the static state, the fog inside the car lights can be stored in a dry environment with humidity <50%RH for 24~36h. Automatically and completely eliminated. For example, the picture below shows the fogging phenomenon.

What are the causes of headlight fogging and water intrusion, and how to solve them? 2

Air humidity is restricted by many factors such as region, terrain, climate, altitude, etc. The average air humidity on a sunny day is around 50%RH. You can increase or shorten the evaluation time appropriately based on this comparison, or simply buy a thermometer and hygrometer.

Now that we have a general understanding of the judgment method, let’s briefly introduce the principle of fogging. The reason why there is water mist in the car lamp is because the water vapor inside the lamp condenses in the form of film and water droplets on the surface of the mask that is lower than its saturation temperature. That is, the water vapor encounters the lamp cover under certain conditions and vapor-liquids on its surface. The result of conversion.

This may sound a bit confusing, but the principle is similar to the fact that windows tend to fog up when the heating is turned on in winter. For those of you who have room for learning, it will be clearer if you look at the schematic diagram below.

What are the causes of headlight fogging and water intrusion, and how to solve them? 3

In contrast, water entering the car lights will be more annoying. If a large area of ​​fog condenses on the inner wall of the lens and the condensation turns into water droplets and accumulates inside the car lamp, it will be difficult to eliminate it even by heating the car lamp, using it repeatedly or drying it in a dry environment. As the temperature rises, the fog will become larger again. area attached to the inner surface of the lens. For example, the picture below shows the phenomenon of water accumulation.

What are the causes of headlight fogging and water intrusion, and how to solve them? 4

Different from fogging, water in the car lights is often caused by poor sealing leading to internal water accumulation. The sealing structure design of automotive lamps generally involves the following three aspects: the sealing design of the lamp itself; the sealing design between the lamp end and the wiring harness end plug-in ; The gap and surface difference between the lamp and the car body. If these three are not handled properly, they may lead to water accumulation problems.

Sometimes we replace the headlights with new ones, and within a day or two of use, we will find fogging and water accumulation in the lampshades. At this time, we need to contact the 4S store as soon as possible.

2. How to solve the problems of fogging and water ingress

Foggy car lights will generally dissipate naturally after a period of time and do not require special treatment. If you feel that this downgrade is not beautiful, you can turn on both the high and low beams of the headlights and use the heat generated by the lights to dry the water mist; or add desiccant or sponge to the back of the lights to avoid this problem. .

Of course, this problem cannot be left entirely to consumers. In terms of product design, for example, changing the vent hole to a one-way breathable film can also reduce moisture entering the lamp cavity; or spraying a layer of low-tension anti-fog coating (or pasting a waterproof breathable film) on the inner surface of the light distribution lens, Beading can also be avoided. So from the original point of view, this problem is not unsolvable. It depends on the design skills and conscience of the manufacturer.

What are the causes of headlight fogging and water intrusion, and how to solve them? 5

▲Going further, the structural design and thermal design of the car lights also avoid low temperatures and flow stagnation areas, and solve the problem of fogging of the car lights.

Obviously, water in the headlights is a more serious problem. For example, it may cause the brightness of the car lights to decrease or short-circuit. If you don't pay attention at ordinary times, it will be dangerous if this problem occurs at night. If the car lights are not on, you will be fined if you are caught (in some areas, you will be fined 300 and 3 points, which is not small) ), or more seriously, it may cause a car accident.

Data shows that although only 25% of a car's driving time is at night or when there is insufficient natural light, 33% of traffic accidents occur in this situation, and about half of the fatal accidents occur. at night.

Although the "Environmental Durability of Road Vehicle Exterior Lighting and Optical Signaling Devices" has clear requirements for the waterproof rain test of vehicle lights, it can also be re-tested during the road test during the product verification stage and the vehicle rain test before the OEM leaves the factory. , but the problem of water in the headlights still cannot be completely avoided.

What are the causes of headlight fogging and water intrusion, and how to solve them? 6

Therefore, if you encounter water accumulation, it is recommended to remove the headlight assembly for inspection to see if there are cracks or other damage to the lights, and then check whether there is a problem with the sealant of the lampshade. For example, aging of the sealing rubber strip will cause elasticity. decline, resulting in loose sealing.

Pay special attention to the fact that the headlights must not be baked directly after water has entered the car. Doing so can easily damage the headlights, because the exterior of the headlights are made of plastic material, and high heat can easily bake the lampshades, and this The damage is mostly irreparable. If no abnormality is found, it is recommended to go to the 4S store for inspection in time and replace the sealing strip and vent pipe of the rear light cover.

Car gathering summary

Due to the limitations of the structure and working principle of car lights, the problem of fogging or water accumulation in cars cannot be completely avoided at this stage, including some luxury cars. However, it can be seen from the above introduction and analysis that products with excellent quality and workmanship will definitely have a lower failure rate.

If you find similar problems in your car, don’t take it lightly, especially water accumulation in the headlights, which should be solved as soon as possible. Of course, behaviors that can damage your car, such as wading, must start with yourself and strengthen your awareness of maintenance.

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