Cabin Air Filter / Purifier: Service and Repair
Dust And Pollen Filter Element, Removing And Installing
NOTE: Change interval for dust and pollen filter. Dust and pollen filter is available in different versions (without and with a filter insert with activated charcoal insert). A dust and pollen filter is currently installed in vehicles with the "Comfort" air conditioning system. A dust and pollen filter is currently installed in vehicles with the "Basis" air conditioning system.
Clean dust and pollen filter area in air conditioner duct before installing a new filter.
On vehicles with driving school equipment, pedals of driving school equipment must be removed if necessary (depending on version, there are service separation points on the training pedals).
Removing
- Move the passenger seat all the way back
- Remove the bolted clips -A- and the insulation mat -B-
- Cover the floor covering in the area under the dust and pollen filter with paper.
- Loosen the retainers -B-, slide the cover -A- in the direction of the -arrow- and remove the cover.
Note: If the retainers -A- can no longer hold the cover -B-, it can be secured with bolts -D- at the mounting points -C-.
- Remove the dust and pollen filter -A- from the A/C unit shaft -B-
Installing
Installation is done in reverse sequence while observing the following.
- Clean the A/C unit via the shaft -B- (e.g. with a vacuum) after removing the dust and pollen filter -A-
- Insert the dust and pollen filter -A- facing the right way (the diagonal -C- in the side toward the fresh air blower -D-).
Note: The flow direction is not specified on the dust and pollen filter -A- for this vehicle.
Dust And Pollen Filter With Activated Charcoal Filter Element
The dust and pollen filter is available in different versions, without and with a filter insert with activated charcoal. A dust and pollen filter with activated charcoal insert is currently installed in vehicles with the "Comfort" air conditioning system. A dust and pollen filter is currently installed in vehicles with the "Basis" air conditioning system.
The dust and pollen filter with additional activated charcoal insert is installed in vehicles with the "Comfort" air conditioning system. These vehicles also have an Air Quality Sensor -G238- installed.
The filter with the activated charcoal insert performs the same task as the dust and pollen filter. It can also filter gaseous pollutants such as ozone, benzene, nitrogen dioxide out of the air inside the vehicle. The basic task of the activated charcoal insert in the dust and pollen filter is to keeep peak loads out of the passenger compartment.
The activated charcoal insert also removed certain gaseous contaminents from the air inside the vehicle. The activated charcoal layer in the dust and pollen filter works different on various pollutants in the air:
Certain pollutants are trapped in the activated charcoal layer.
Others are converted into harmless compounds like in a catalytic converter.
For the remainder, the activated charcoal functions as a condenser. When the load increased, pollutants are first absorbed until a certain saturation point is reached. If the amount of pollutant decreases, the activated charcoal continuously releases the absorbed particles.
Because the activated charcoal layer also absorbs a portion of the gaseous particles permanently in addition to dust and pollen, the filter may need to be changed earlier then specified when under the following conditions.
- When operating the vehicle in areas with continuous heavy air pollution. The activated charcoal layer in the dust and pollen filter is saturated earlier then intended.
- When operating the vehicle with the "automatic recirculation" function switched off most of the time.
On vehicles with an air quality sensor -G238-, the air conditioning system should be operated in the "automatic recirculation" function as much as possible. However, if it is necessary or desired to switch the function off, observe the following:
- The activated charcoal layer in the dust and pollen filter will become saturated after a certain amount of time
- A saturated filter cannot absrb any more pollutants so they will enter the vehicle.
The basic task of the activated charcoal insert in the dust and pollen filter and the air quality sensor -G238- is to keep peak loads out of the passenger compartment. Keep the following in mind:
- If a vehicle is driven in an area with relative clean ambient air (with little gaseous pollutants in the air), the change over from fresh air mode into recirculating mode at a different time then when travelling in an area with high constant level of pollutants..
- The switch from fresh air mode to recirculation mode always takes place whenever the amount of pollutants increases, regardless of what the constant level is (e.g. when driving in the exhaust cloud of a diesel truck).