Cabin Air Filter / Purifier: Service and Repair

Dust and Pollen Filters, Removing and Installing






- Press in quick-lock -A- slightly and turn approx. 90° (1/4 turn).


NOTE:
The two dust and pollen filters must be replaced at certain intervals and always both filters at the same time
- With the introduction of the sensor for air quality -G238- a revised dust and pollen filter is installed. This filter consists of an additional filter insert with active charcoal.
- The filter with its activated charcoal insert functions as a dust and pollen filter, but can also filter out gas forming pollutants such as ozone, benzol, nitrogen dioxide etc. from the air flow.
- The activated charcoal filter collects gas forming pollutants which flow through the air until the fresh air flap has closed and the A/C function switches to the recirculating air mode. The change-over from fresh to circulating air mode occurs as soon as the sensor for air quality -G238- recognizes gas forming pollutants in the surrounding air via A/C control head -E87- (the function "Automatic air recirculation" must be selected).
- The activated charcoal layer in the dust and pollen filter affects the pollutants in the air differently Specific pollutants are bound securely to the activated charcoal layer, while others are changed in a catalyst into non- damaging particles. For the remainder the activated charcoal works like a condenser. When the load increases, the pollutants are taken up only to a specific saturation point, removing that percentage of pollutants, continuously handing off those particles to the activated charcoal layer.
Since the activated charcoal layer binds one part of the pollutant particles, it is important to change the dust and pollen filter earlier than specified:
- When operating the vehicle in areas of heavy air pollution.
- When operating the vehicle with 'Automatic air recirculation" shut off
- For vehicles without the sensor for air quality -G238- and without the "Automatic air recirculation" function.

For vehicles with the air quality sensor the A/C should, if possible, always be in the "Automatic air recirculation" mode. If it is necessary or requested to shut off the function, the following must be noted:
- The activated charcoal layer in the dust and pollen filter can become saturated over time.
- A saturated filter cannot collect anymore particles and will hinder the flow process.

The essential function of the dust and pollen filter and the sensor for air quality is that it removes peak pollutants from the passenger compartment. Therefore, the following must be noted:
- It is recommended to change-over from fresh to Automatic air recirculation mode while the vehicle is being driven through an area with relatively clean recirculating air (low concentration of pollutants in the air) rather than when in an area with a higher concentration of pollutants (e.g. industrial areas).
- The changeover from fresh to recirculating air occurs independent of the base level of pollutants, but always occurs when the concentration of pollution increases (e.g. when driving through an exhaust cloud of a diesel truck).

The charcoal filter can be installed on all vehicles (including vehicles without the sensor for air quality). However, for these vehicles the same limitations apply as when operating the A/C with the "Automatic air recirculation" function switched off