Supersedes Technical Service Bulletin Group 94 number 12-91 dated
October 24, 2012. Considerable moisture present in headlamp. The moisture disappears only after extended drives (greater than 10
minutes). No external damage to headlamp which could introduce moisture. Humid air settles on the inside of the glass, causing moisture to appear on the inside of the headlamp lens. Because of the headlamp circulation system, outside air is allowed to flow through the headlamps. The open, water-protected ventilation system (needed for pressure compensation) creates different ? climate zones? inside the headlamp, where the lens is either warmed up by the light or cooled down by passing air. When high air humidity and temperature differences exist between the inside of the headlamps and the outside,
condensation can form on the inside of the lens, especially in cold and wet weather. The moisture in the headlamps can be compared with condensation on the windshield, which is cleared by the "defroster vent". This moisture buildup can happen for example: after a car wash, after steam cleaning of the engine or the front end, or after overnight temperature changes. This condition is more easily visible with headlamps made from clear glass. The moisture is an optical condition
which does not affect the headlamp function (light performance) and does not lead to corrosion nor does it lead to damage of the internal headlamp parts. This condition is common to all exterior vehicle lights, and can occur on every headlamp, fog lamp, or rear lamp.
