Standard Procedure - Headlamp Unit Moisture Clearing

Some customers may report that on occasion, vehicle exterior lamp assemblies are fogged with a light layer of condensation on the inside of the lenses. This may be reported after the lamps have been turned on and brought up to operating temperature, turned off, and then rapidly cooled by cold water (such as rain, or the water from a car wash). Lens fogging can also occur under certain atmospheric conditions after a vehicle has been parked outside overnight (i.e., a warm humid day followed by clear cool night). This will usually clear as atmospheric conditions change to allow the condensation to change back into a vapor. Turning the lamps on will usually accelerate this process.

A lamp that exhibits condensation/fogging should be evaluated in a service bay environment by first drying all water from the outside surface of the lens and operating the lamp for 20 minutes. If the condensation/fogging has begun to clear from the lamp lens after 20 minutes with the lamps operating, this indicates the lamp sealing has not been breached, and the lamp does not need to be replaced.

If the condensation/fogging has not begun to clear after 20 minutes with the lamps operating, or the lamp has large amounts of water droplets visible on most internal surfaces, this indicates a problem with the lamp sealing that has allowed water to enter the lamp. In this instance, the customer is also likely to report that moisture in the lamp is always present and never disappears. A lamp that exhibits internal moisture permanently should be replaced.