What causes headlights to sweat from the inside and how to fix it
Content
Forming a powerful light beam to illuminate the area in front of the car is not as easy as it might seem. In addition to brightness, the beam should have defined boundaries, revealing its own lane and roadside from the darkness, and not the eyes of oncoming drivers.
The light device has no right to overheat in any conditions, consume too much energy, and at the same time must remain within the budget that is reasonable for this price category of the car.
It turns out a rather thin and complex optical device, the properties of which can be distorted even by a certain amount of water vapor in the case.
The headlight unit in the car
In many headlights of modern cars, a number of lighting devices are combined:
- high beam lamps - the most powerful and important in terms of temperature changes;
- low-beam filaments combined in the same bulb with them, or made in the form of separate lamps, but located in the same headlight housing;
- separate or combined reflectors (reflectors) of high and low beam, serve to return radiation from the rear hemisphere forward;
- refractors and lenses that form the direction of the light beam, if this is not provided for by the design of the reflector;
- additional light sources, lamps for overall lighting, direction indicators and alarms, daytime running lights, fog lights.
In any case, the headlight has a front transparent glass that outputs the light flux, and a reflector near the rear wall of the housing.
The optical properties of these elements are chosen very precisely, therefore, when water drops hit, additionally and unpredictably refracting the rays, the headlight turns from a regular working light device into a primitive flashlight, which is also reduced due to effective power dissipation.
Without ventilation, it is difficult to combat this effect. When using incandescent lamps, a significant amount of energy is released in the form of heat. The air inside the case heats up, expands and needs to be vented.
To avoid the effects of pressure buildup, headlights usually have two valves, an intake and an exhaust. Sometimes they are combined together.
In any case, such valves are called breathers. There are similar devices in other units of the car, engine, gearbox, drive axles.
Through the breathers, the headlight housing is ventilated. The air changes in small portions, which gives hope to eliminate the massive ingress of water, for example, in the rain or when washing the car. But not everything always works properly.
Causes of fogging optics in a car
When the fogging of the glass from the inside quickly disappears after the headlight is turned on and the temperature rises, then this is a completely regular phenomenon, which is useless to deal with lamps with ventilation.
Yes, and this does not always happen, a lot depends on the humidity of the air that the headlight “breathed” after turning off and cooling, or on the speed at which gas exchange occurs.
- The ventilation outlet valve may become dirty, after which moisture in the headlight housing will accumulate, having no way out. Similarly, it happens with an unsuccessful arrangement of breathers. Headlights have long ceased to fulfill their sole purpose of illuminating the road. Now this is an important design element, and accordingly the shape is not optimized in any way in terms of ventilation.
- With the exception of the routes provided, free exchange of air must be excluded. The body of the headlight heats up unevenly, so ventilation must be carried out according to the results of studies and tests to minimize fogging. Housing depressurization in the form of cracks or defects in seals will lead to the ingress and accumulation of unaccounted for moisture.
- The owner can always, against his will, increase the flow of water into the body of the device. To do this, it is quite enough to ensure its presence at the inlet breather when cooling. A change in temperature will draw in the right amount of moisture, sufficient for its long-term elimination with the available means. It will look like a complete failure of ventilation. But in reality it will pass with time.
That is, there are two cases - when you need to take action and "it will fix itself." Strictly speaking, there is also a third one - a design error, which has usually already been learned to correct by the collective mind on the specialized forums of some car models.
What to do if headlights sweat
Almost all measures here are available for independent execution.
Breather cleaning
Breathers can be closed with membrane partitions or free. In the first case, the membrane will have to be removed along with the body and blown with compressed air in the hope that this will help. Or replace it with a suitable substance, for example, synthetic winterizer.
A free breather can be cleaned by any known method, for example, with a thin wire or the same compressed air. Sometimes it helps to install homemade breathers in better places.
Violation of the integrity of the sealant
Re-gluing the glass and body seals is a rather voluminous procedure. It is necessary to soften with heat and remove the old sealant, degrease and dry the headlight, glue it with a new one.
A special silicone-based headlight sealant is used, but sometimes the usual one does a good job, for forming gaskets. It is only necessary to avoid acidic ones.
Cracks
Cracks in a plastic case are quite easy to solder, having previously studied this technology and practiced on a specific type of plastic. Not all of them are thermoplastic, but the same sealant can be used.
Often cracks and leaks appear not in plastic, but in elastic seals of lamp sockets, service hatches and correctors. These items can be replaced. But in a severe case, you will have to put up with fogging or change the headlight assembly.
Cracks are not always easy to find. You can use the technology of finding punctures in tires, that is, immerse the headlight in water and observe the appearance of bubbles.
What causes fogging headlights
A misted headlight is considered faulty with all the ensuing consequences. It is impossible to move in the dark with it. Drivers of oncoming cars are endangered due to dazzle, and the owner of a faulty car himself does not see the road well. This is expressly prohibited by the regulation.
But even if you take the time to dry, the constant penetration of large amounts of water with slow removal will lead to corrosion and destruction of reflectors and electrical contacts. Increased contact resistance at high current consumption will cause overheating and deformation of the plastic.
The headlight can completely fail. All this is much more serious than the unpleasant appearance of a car with cloudy glasses of lighting devices. It is not worth delaying in identifying and correcting the problem.
