Field Remedy: 2220

Remedy:

In case of a customer complaint the following items have to be checked
to avoid an unnecessary rear lamp exchange.

1. If heavy condensation is present (drops forming inside on the lens) 
the correct position of the knurled screw, the sealing of the rear 
lamp as well as the correct fixing of the first aid  box (so that the 
ventilation openings are free, see picture I, arrow) have to be
checked.

2. In addition there should be no humid or wet objects inside the
vehicle.
Should any condensation in the light-technically effective emergence 
surface, (see picture II, 1) exist after having carried out above
mentioned checks, the sealing has to be replaced. Condensation on the
rest of the lense surface (not effective light-technically surface,
see picture II, 2) can occur and is allowed. 

Rear lamps should be replaced only in case of water leakage or if 
clear water traces are visible after drying of the rear lamp on the 
inside of the lens.

Aid for Argumentation:
The following description may be used for explanation to the customer.
As a consequence of the open ventilation system which is needed for 
pressure compensation, different "climate zones" occur within the rear 
lamps. As a result the lens is fogging.
In detail very warm areas occur in a rear lamp with relatively cooler 
areas on the other side. The heating is generated by the heat emitted 
by the lamp source, the cooling of the lens is caused primarily by the 
slipstream. After switching off the lamp source, the air in the rear 
lamp cools down slowly. This causes air saturated with moisture to be 
drawn from outside into the inside of the rear lamp housing.
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 damp weather.

Condensation can also occur after using a car wash, steam cleaning
the back of the vehicle and if temperature changes occur during
the night etc.

Due to usage of lenses with a clear glass appearance (which can also 
be tinted) this phenomenon is more obvious than on lenses with a 
structure. The condensation in rear lamps is caused by a physical
process and does not affect the optical function of the rear lamp
(light output) in any way. The phenomenon of condensation can occur
on any rear lamp including those of our competitors. Hence the rear
lamps must not be replaced to rectify this condition since no
technical defect exists.

Please also refer to the owner's manual "Astra" where this phenomenon
is described as well.

It should be noted when explaining the matter with customers that the 
time pattern of the heat dissipation process for condensation is 
extremely dependent on the temperature in the immediate area and the 
relative humidity of the air.