If complaints are received about the above, this does not necessarily mean there is a fault in the lighting. When the cover lens fogs up, the photometric output area should dry within a certain period after the light bulb has been switched on. However, this process can happen more or less quickly depending on the ambient temperature and relative air humidity. This process is completely in line with normal physical laws and completely harmless from a technical point of view, since the reflector is protected against the influence of fogging.
When the light bulb is switched on, the air inside the light heats up. The expanded, heated, and dry air is displaced out of the housing of the rear combination lamp through the ventilation slits. After the light bulb has been switched off, the air in the rear combination lamp slowly cools down again. This causes saturated humid air from outside to be “sucked” into the light interior. This can lead to condensation on the inside of the cover lens on account of high air humidity and greater temperature differences inside the light. This condition occurs more frequently in the cold months and in humid weather. However, if there is so much fogging that water drops form on the cover lens (see Figure 1) or water even accumulates in the lower area of the light (see Figure 2), the seal should be checked for damage and replaced if necessary.
Equally, any “blockage” of the light ventilation openings should be checked. The light can be blasted with oil-free compressed air to dry it out. If water still accumulates in the light after this process, the light has to be replaced.