Headlamp fogging is the condensation of moisture on the cooled inner surface of the glass. This happens when there is an excess of moisture or due to the lack of ventilation of the headlight housing. Of course, optics manufacturers try to protect the headlight as much as possible from water penetration, but 100% protection is difficult to achieve. Headlights fogging occurs in both new and old cars.
Most modern cars are equipped with plastic light optics, microdamages on the plastic and sealant of which are not noticeable. However, in a sink with high water pressure, moisture is still “forced” through the cracks. In addition, moisture penetration occurs during heavy rain and when forcing deep puddles when the headlights are on. In this case, the headlights are sharply cooled, a vacuum is formed inside it, and moist air is sucked in through the existing holes (microcracks). High humidity appears inside the case and when the headlights are turned off, their glasses fog up. If one of the light elements fogs up, and the rest do not, this indicates a lack of ventilation in it or a loss of tightness. The reason is a factory defect or damage during operation caused by mechanical stress on the surface of the optics and violations of the sealing joints of lighting devices. Headlights with halogen lamps rarely sweat, since such a light source emits a large amount of heat, and the optics are equipped with ventilation holes. Hot air is discharged through a special channel in the upper part of the case, and cold air enters through the lower opening. The latter, in combination, is also a drainage channel for condensate drainage. Even when it is clogged, the headlights rarely sweat: during operation, halogen lamps heat up to 700 ° C and dry out all the air inside the body. Round unified headlights with two-filament bulbs sweat more often. But this does not harm them. First of all, because the aluminum reflector, as a rule, is reliably protected from corrosion. Secondly, because moisture first condenses on the inner surface of the glass, and only then on the reflector. To dry a fogged headlight, it is enough to turn it on while parking. Not receiving cooling by the oncoming air flow, the glass and the inner cavity of the headlamp will warm up and the condensate will evaporate, partially leaving as a result of the expansion of the air. To prevent this phenomenon, you should regularly clean the ventilation ducts of the lighting devices, and also drill 2-3 additional holes with a diameter of 2-3 mm in the plastic (from the inside of the headlight). In this case, it is important that the direction of the holes is from bottom to top. This will exclude the ingress of water into the headlight during rain and when washing a car. It is possible to detect microdamages of the headlights and their seals only by filling the inner surface of the lighting fixture with colored gas under pressure using special equipment. Elimination of cracks occurs with the help of special polymer compounds for the restoration of optics or with the help of specialized adhesives. In some cases, sealants restore violations of the sealing joints.
