Moisture in your car's headlights can make them appear foggy, affecting the brightness of the lights. When condensation gathers behind the headlight lens, it can reduce visibility at night, and over time it may cause damage that will result in the need to replace the entire headlight. It is possible to remove moisture from your car's headlights in your own garage. Depending on the type of vehicle you own, this usually involves a few simple steps.
Open the bonnet and remove the back cover plate of the headlight lens. You might need to use a screwdriver to pry the plate open. Some models of cars require that you also remove the bumper to remove headlights. Check this before you begin, and make sure that you are able to remove the bumper by yourself.
Wiggle the cover plate gently, from side to side, to pull it off.
Remove the headlight bulb but be careful not to touch the glass of the bulb, as oils from you hand will cause it to burn out prematurely.
Disconnect the wiring from the headlight, and remove any rings or clips that might be holding the headlight in place.
Remove the headlight. Gently dry the parts of the headlight with a clean towel, if you see moisture. This includes the cover plate, wiring and clips or rings. Do not rub the bulb dry. Allow it to dry on its own.
Pull out the headlight lens. Some headlight lenses are glued in place. If this is the case, use a hair dryer to heat the silicone glue (it softens the glue), then remove the lens.
Dry off any water on the inside of the headlight lens, and wipe dirt and grime away, using a clean towel.
Apply polishing compound (purchased at an auto supply store) to the lens, using a damp towel. Polish by scrubbing, but be careful not to damage the lens.
Polish again, using the polishing compound, until the lens is clean.
Spray glass cleaner on the lens and wipe away with a dry towel. This will remove leftover polish residue. You might have to apply the glass treatment a couple of times to wipe away the entire residue.
Dry the headlight lens, using a clean towel.
Replace the headlight lens and reconnect the headlight wiring. If you had to heat the silicone to remove the lens, reapply a bead of RTV silicone around the lens before replacing. You can purchase silicone glue at a hardware or auto supply store.
Replace and rings or clips that you removed and reattach the cover plate.