Air Quality Sensor Function

• The Air Quality Sensor -G238- detects the pollutants in the surrounding air (mostly gasoline and/or diesel exhaust gases) and switches the Climatronic Control Module -J255- to recirculating air mode.
• Climatronic control module detects the type and intensity of air pollution at signal from the Air Quality Sensor. Depending on the outside temperature and the intensity of air pollution, the Climatronic control module then decides:

- At an outside temperature greater than approximately +2 °C (36 F) the recirculating air mode is switched on when there is only a slight increase in pollutants in the ambient air.

- At an outside temperature between approximately +2 °C and approximately -8 °C, the change over to recirculating air mode only occurs at a sharp increase of pollutant concentration, during which the compressor is switched on simultaneously.

- At an outside temperature less than approximately -8 °C, the change over still occurs only at a sharp increase of pollutant concentration and then only for approximately 15 seconds (compressor is not switched on).

- If the pollution concentration in ambient air drops, the climate control system switches over to the fresh air mode.

• Automatic recirculating air mode can be switched off at any time. If the function is active, the A/C compressor is switched on with a request for automatic recirculating air mode and also when the outside air temperature is below +2 °C. If the temperature is below -8 °C, then it is not possible to sue the A/C compressor.
• At setting automatic air recirculation on Climatronic control module, compressor can be switched on also by switching on recirculating air manually (via recirculating air button Umluft  ) up to a temperature of approximately -8 °C,
• To ensure that the A/C does not operate constantly in the recirculating air mode in areas with a consistently higher pollution, the sensor is self learning (it adjusts its sensitivity to the environmental conditions).
• If outside air pollution load remains high for longer period of time, the sensor starts to adapt itself to the changing environmental condition through an adaptation program (learning program), the air recirculation request in evenly polluted ambient air is therefore generally shorter than 12 minutes. If a succession of peaks in the polluted air is detected, the air conditioning system can operate over a longer period of time in recirculated air mode.
• A certain amount of time is required for repositioning of the air conditioning system doors. In the event that a sudden increase in pollutants is encountered (e.g. when driving through a diesel exhaust cloud) gaseous pollutants can be taken in with the fresh air into the passenger compartment until the door can be closed. For this reason, a dust and pollen filter is installed with a charcoal layer. A filter that is saturated with pollutants is no longer effective and needs to be replaced, refer to DUST AND POLLEN FILTER .
• In order to avoid frequent shifting of the fresh /recirculating air doors, a slight increase of pollutants in the ambient air will not allow for immediate shifting (the sensor does not send a request to Climatronic control module). The filtering of the charcoal insert in the dust and pollen filter will be sufficient, refer to DUST AND POLLEN FILTER WITH ACTIVATED CHARCOAL INSERT .
• In order to avoid frequent shifting of the fresh/recirculating air doors, the requirement from the sensor for Automatic air recirculation mode remains for at least 25 seconds (minimum duration period), even if the pollutant concentration is so far reduced that recirculating air mode is no longer necessary.
• If the A/C compressor is shut-off (e.g. in Econ mode), the maximum duration of the Automatic recirculating air mode is limited to approximately 15 seconds by Climatronic control module to avoid windows from fogging up. Depending on the control head version, Econ is on when the ECON  button lights up and the AC  is off.
• So that fogged windows are cleared as quickly as possible, Climatronic control module does not permit recirculating air operation during the Defrost operating mode.
• After the ignition is switched on, Air Quality Sensor requires approximately 30 seconds to be operational (warm-up time). During this time there is no requirement from the sensor to Climatronic control module for Automatic recirculating air mode.
• The Air Quality Sensor contains a highly sensitive electronic component which can be damaged if it comes in direct contact with solvents, fuels or chemicals. For this reason, do not install sensors that may have come into contact with these substances.