Remedy:
In case of customer complaint, the following items have to be checked
to avoid unnecessary replacement of headlamps.
If there is fogging on the headlamp lens, also designated condensation
below, the emergence surface on the lens, which is active as regards
lighting technology, must be clear after traveling for approx. 20 minutes
with the dipped beam switched on. The remaining surfaces of the lens can
and may still be covered with condensation after this.
It should be noted when discussing the matter with customers that the time
pattern for the dissipation process for condensation is extremely dependent
on the temperature in the immediate area and the relative humidity of the
air. In a situation of this kind, AOAG will not accept the costs for
replacing headlamps.
If heavy condensation is present (drops forming on the lens) the covering
caps and seals on the headlamp casing must be checked and the lens should
have oil-free compressed air blown over it. The effectiveness of the
measures undertaken should be checked by further observation.
If water is penetrating into the headlamp via damaged seals, bonded joints
et cetera, the corresponding repairs should be undertaken (change seal,
replace headlamp, ...).
If headlamps, which prove to be in good order according to the manufacturer's
test stipulations, are submitted under the warranty, you may be charged for
them. Please contact your national service center in problem situations.
Aid for Argumentation:
The following description may be used as an aid to argumentation in discussions
with customers.
As a consequence of the open ventilation system, which is, however, protected
from spray and which is needed for pressure compensation, different "climate
zones" occur within the headlamp, resulting in fogging of the lens. Thus, for
example, very warm areas occur in a headlamp with relatively cooler areas on
the other side. The heating is generated by the heat emitted by the light
source, the cooling of the lens is caused primarily by the slipstream. As a
consequence of the labyrinthine design of the ventilation apertures, expanding
heated dry air is forced out of the headlamp casing. After switching off the
light source, the air in the headlamp cools down slowly. This causes air
saturated with moisture to be drawn from outside into the inside of the
headlamp casing.
In the presence of high humidity and high temperature differences between the
inside of the housing and the environment, this situation can cause condensation
to occur on the inside of the lens, especially in cold times of the year and in
damp weather.
Condensation can occur, for example, after using a car wash, steam cleaning the
engine and the front of the vehicle, if temperature changes occur during the
night, etc.
Even the smallest imaginable moisture in the air inside the headlamp can be
precipitated on the lens, especially in the "subsequent heating phase", during
which the back of the headlamp is heated because the engine is still warm, but
at the same time the lens is being cooled down by cold outside air. Since
lenses with a clear glass appearance are now being used, which may also be
tinted, this phenomenon is more obvious than on lenses with a structure.
The process involved in condensation in headlamps is caused by physics and
does not affect the optical function of the headlamp (light output) in any way.
Neither can the condensation cause any corrosion in the headlamp.
The phenomenon of condensation can occur on any headlamp, including those of
our competitors, because it is caused by a physical process. Changing the
headlamp is therefore unacceptable because no technical defect within the
meaning of the warranty is involved.