A3 L4-2.0L Turbo (BPY) (2006)
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Climate Control Exhaust Gas Sensor: Description and Operation
Air Quality Sensor
‹› Air Quality Sensor (G238) detects pollutants in the ambient air (mostly gasoline and or diesel exhaust) and orders A/C control head Climatronic
Control Module (J255) to switch the air conditioning system to recirculating air mode.
‹› A/C control head Climatronic Control Module (J255 ) detects the type and intensity of air pollution at signal from Air Quality Sensor (G238).
Depending on the outside temperature and the intensity of air pollution, A/C control head Climatronic Control Module (J255) then decides:
- At an outside temperature greater than approx: +2 °(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 ° and approximately -8°, 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° the change over still occurs only at a sharp increase of pollutant concentration and then only for
approximately 15 s (compressor is not switched on).
- If the pollution concentration in ambient air drops, the climate control system switches over to the fresh air mode.
‹› The function "Automatic air recirculation" can be switched off at any time. If the function is active and a request for "Automatic air recirculation"
is present the A/C compressor is also switched on when outside temperatures are lower than +2°. Compressor operation is not possible with
temperatures lower than approximately -8 C.
‹› At setting "automatic air recirculation" on A/C control head Climatronic Control Module (J255), compressor can be switched on also by switching
on recirculating air manually (via recirculating air button Recirculation) up to a temperature of approximately -8°.
‹› 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 ] See: Cabin Air Filter/Service and Repair/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 A/C control head Climatronic Control Module (J255)). 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 ] See: Cabin Air Filter/Service and
Repair/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 A/C control head Climatronic Control Module (J255) 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, A/C control head Climatronic Control Module (J255) does not permit recirculating air
operation during the "Defrost" operating mode.
‹› After the ignition is switched on, Air Quality Sensor (G238) requires approximately 30 seconds to be operational (warm-up time). During this time
there is no requirement from the sensor to A/C control head Climatronic Control Module (J255) for " Automatic recirculating air" mode.
‹› The Sensor for Air Quality (G238) 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.