Air Quality Sensor G238 Functionality - Audi Q7 2007 Repair Manual

Audi Q7 2007 ➤
Heating, Ventilation and Air Conditioning - Edition 04.2013
Terminal assignment on connector to Air Quality Sensor - G238-
-A-
1 - B+ (terminal "15")
2 - Ground (terminal "31")
3 - Signal wire to Climatronic Control Module - J255- front A/C
control head.
Note
The Air Quality Sensor - G238- measured value is displayed in
the Climatronic control module - J255- front A/C control head. The
square wave signal cannot be evaluated using workshop equip‐
ment. Use the Vehicle Diagnostic Tester via the "Guided Fault
Finding" function.
Installing
Install in reverse order of removal. Note the following:
♦ The Air Quality Sensor - G238- contains a highly sensitive
electronic component which can be damaged if it comes in
direct contact with solvents, fuels or chemicals. Therefore do
not install sensors that were previously stored e.g. in tool box‐
es.
5.5 Air Quality Sensor - G238- Functionality
♦ The Air Quality Sensor - G238- is installed only on vehicles
with a "Comfort" version A/C system.
♦ The Air Quality Sensor - G238- detects pollutants in the am‐
bient air (mostly gasoline and or diesel exhaust) and orders
the Climatronic Control Module - J255- front A/C control head
to switch the air conditioning system to recirculating air mode.
♦ Depending on setting in MMI (Multi Media Interface), the sun‐
roof closes as soon as the Climatronic Control Module - J255-
front A/C control head switches over to air recirculation mode
(automatic air recirculation via the Air Quality Sensor - G238-
or manual air recirculation by operating the air recirculation Protected by copyright. Copying for private or commercial purposes, in part or in whole, is not
permitted unless authorised by AUDI AG. AUDI AG does not guarantee or accept any liability
button). This function is equipment-dependent, its introduction
with respect to the correctness of information in this document. Copyright by AUDI AG.
has not yet been finalized. Refer to the Owner's Manual.
The Climatronic Control Module - J255- front A/C control head
detects the type and intensity of air pollution at signal from sensor.
Depending on the outside temperature and the intensity of air
pollution, the Climatronic Control Module - J255- front A/C control
head 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 (36°
F) and approximately -8° C (17.6° F), the change over to re‐
circulating air mode only occurs at a sharp increase of pollu‐
tant concentration, during which the compressor is switched
on simultaneously
– At an outside temperature less than approximately - 8° C
(17.6° F), 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 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 "Auto‐
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Rep. Gr.87 - Air Conditioning