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| Position spray attachment -A- of test gas canister over air inlet of air quality sensor -G238--B- (with version “2” of air quality sensor -G238-). |
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| Press spray knob -C- of test gas canister for approx. 1 second. |
Note | t
| There are different air quality sensor -G238- housings. Version “1” was fitted at the start of production. This sensor is gradually being replaced by version “2”, however the mode of operation is identical. |
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| The test gas canister is filled with pure oxygen with a specific nitrogen oxide component. |
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| The air quality sensor -G238- also reacts when exposed to cigarette smoke or cigarette lighter gas (gas is heavier than air, the air quality sensor -G238- must therefore be removed and turned round). |
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| Read off display in zone “4”. |
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| “10” (“Automatic air recirculation mode” requested, request met, air conditioner switches to recirculated-air mode) |
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| Wait briefly (approx.1 minute, depending on amount of test gas sprayed onto air quality sensor -G238-). |
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| Read off display in zone “4”. |
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| “00” (no request for “recirculated-air mode”, air conditioner in fresh-air mode) |
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| “60” (Partial recirculated-air mode) |
Note | To stop the recirculated-air/fresh-air flaps being switched too frequently, an air quality sensor -G238- request for “automatic recirculated-air mode” is applied for at least 25 s (minimum dwell time) even if the pollutant concentration in the air has decreased to such an extent that recirculated-air mode would no longer be necessary. |
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| Actuate windscreen wash/wipe switch until washer pump -V5- has conveyed fluid for approx. 2 s. |
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| Read off display in zone “4”. |
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| “30” (“Recirculated-air mode” requested on account of windscreen washer system, air conditioner switches to recirculated-air mode for approx. 10 sec.) |
Note | The request for “recirculated-air mode” during windscreen washer system operation is not implemented with all versions of the operating and display unit, Climatronic control unit -J255-. |
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| Read off display in zone “4”. |
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| “00” (no request for “recirculated-air mode”, air conditioner in fresh-air mode) |
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| “60” (Partial recirculated-air mode) |
Note | t
| Depending on the composition of the windscreen washer fluid, the air quality sensor -G238- may detect air pollution and request “Automatic air recirculation”. |
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| If switching to recirculated-air mode does not take place on actuating windscreen wipe/wash switch, check operation of automatic intermittent wipe/wash relay -J31- if applicable (“windscreen wash” information is received via the convenience data bus system from the steering column electronics control unit -J527-) (Reading measured value block, display group “018”) → Chapter. |
| Proceed as follows if the air quality sensor -G238- functions properly in this test but a customer complaint has been received: |
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| Check for contamination of dust and pollen filter. |
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| Connect up vehicle diagnostic, testing and information system -VAS 5051A- for example and select function “08 Reading measured value block” for air conditioner. |
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| Enter display group number “014” and read off displays in zones “3” and “4”. |
Note | t
| A second person is required to read out the values displayed whilst driving. |
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| Pay attention to safety precautions → Chapter. |
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| Perform a test drive, starting in an area with a relatively clean ambient atmosphere (system operating in fresh-air mode) and then proceeding to an area where the atmosphere is polluted (e.g. uphill road with lorry traffic). |
Note | t
| The display in zones “3” and “4” in display group “014” must change, for example, on driving through a cloud of diesel emissions → Chapter. |
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| Also pay attention to the notes on the dust and pollen filter → Chapter and on operation of the air quality sensor -G238- → Chapter. |
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