Most modern vehicles is equipped with a plastic with optics, pinholes in the plastic and Hermetica which is not noticeable. However, washing with high pressure water, moisture still "pushed" through the cracks. In addition, the penetration of moisture occurs during heavy rain and in crossing deep puddles when the lights turned on. While the spotlight is suddenly cooled, the vacuum is formed, and moist air is drawn in through the existing holes (microfractures). Inside the case there is increased humidity and when you turn off the headlights their glasses fogged up.If one of the light elements fog up, and the other is not, it speaks to the lack of ventilation in it or on loss of seal. The reason – a manufacturing defect or damage during operation due to mechanical effects on the surface of optics and breach seals lighting.Headlights with halogen bulbs are sweating rarely as a source of light emits large amounts of heat, optics and vented. The hot air is routed through a special channel in the upper part of the body, and the cold comes through the bottom hole. The last part is a drainage channel for draining the condensate. Even when it is clogged lights sweating rare: halogen lamps heat up to 700оС and dried all of the air inside the case.Unified round headlights with dvuhvetvevym incandescent sweat more often. But it does not bring harm to them. First, because the aluminum reflector, as a rule, is protected from corrosion. In the second place, because the first condenseries moisture on the internal glass surface and the reflector.To dry the sweaty spotlight enough to turn it on while stationary. Not getting the cooling RAM air, glass and the internal cavity of the lights warms up and the condensation to evaporate, leaving out partly as a result of expansion of air. To prevent this phenomenon should regularly clean the ventilation ducts, lighting fixtures, and to neverlet in the plastic (inside lights) 2-3 additional holes with a diameter of 2-3 mm. it is important that the direction of the holes were from the bottom up. This will prevent water from getting inside the headlights during rain and when washing the car.To detect microdamages lights and their seals, only filling the inner surface of the lighting device a colored gas under pressure using special equipment. The removal of cracks takes place using a special polymer compounds for the restoration of the optics or by using specialized adhesives. In some cases, sealants restore the breach seals.