Lighting - Moisture Accumulation In Exterior Lamps
94 Exterior lights, moisture accumulation
94 12 92
2012749/11
October 24, 2012.
Supersedes Technical DIAGNOSIS AND REPAIR Group 94 number 11-52 dated October 11, 2011 for reasons listed below.
Affected Vehicles
Condition
Condensation is visible on the inside of the headlight, taillight, fog light, side marker light, front turn signal, daytime running lights, or third brake
light lens.
Technical Background
Damp air settles on the inside of a cold lens, which creates condensation.
The headlight circulation system allows air from the outside to flow through the headlights. This open water-protected ventilation system (needed for
pressure compensation) creates different climate zones in the headlight: very warm areas, where the lens is warmed up by the light, and relatively
cool areas, where the lens is cooled down by the air flow.
Considerable differences in humidity and temperature between the inside and the outside of the headlights, even while driving, can lead to
condensation. This is especially true in cold and wet weather, but it can also happen after a car wash, after steam cleaning the engine or the front end,
with overnight temperature changes, etc. This phenomenon is more visible on lenses made of clear glass than on lenses with patterns. The moisture
does not affect the headlight function (light performance) and does not lead to corrosion or other damage to headlight parts.
Production Solution
Not applicable.
Service
For headlights, the affected lens surface should be clear after approximately 10 minutes of light operation, although the entire lens surface may not
clear. The clearing process depends on the outside temperature and the humidity.
In cases where water droplets have formed on the inside of the lens or water has collected at the bottom of the light assembly, check for leaking seals
and/or cracks in the lens or light assembly. If no damage is found, use compressed air (less than 30 PSI) to clear the lens.
On light assemblies with LED lights, e.g. S6 daytime running lights, the LED lights do not emit enough heat to clear the moisture from the lens. Only
the pressure difference of the ventilation system provides the air flow to clear the moisture on the inside of the lens. The design of the ventilation
system on these types of lights will ensure the lens is clear after a few miles have been driven.
For Audi Q7, please see TSB 2028277 94 Moisture accumulation in headlamps for the installation of headlight ventilation valves. Do not replace
light or lens assemblies for these conditions.
Audi A4 Quattro Sedan (8K2) L4-2.0L Turbo (CAEB) Page 4
Warranty
This TSB is informational only and not applicable to any Audi warranty.
Additional Information
All part and service references provided in this TSB are subject to change and/or removal. Always check with your Parts Dept. and service manuals
for the latest information.
