Preparation Audi A8 D2

Preparation

1. Check DTC memory.

Scheme 27

If a DTC is recognized, repair and eliminate all malfunctions. See DIAGNOSTIC TROUBLE CODE (DTC) MEMORY, CHECKING (FUNCTION 02) .

1. Remove plenum chamber cover.

Scheme 28

1. Switch ignition on.
2. Set A/C control head -E87- to "Auto" operating mode.
3. Start engine (compressor on).
4. Press button for "Automatic air recirculation" (lamp in -A- button comes on).
5. Wait 30 seconds (warm-up time of sensor for air quality -G238-).
6. Connect VAG 1551 Scan Tool (ST) to 16-pin Data Link Connector (DLC) using VAG 1551/3 adapter cable. See «VAG 1551 (VAG 1552) SCAN TOOL (ST), CONNECTING AND SELECTING FUNCTIONS»(/audi/a8/d2-1994-1999/remont/heated-glassdefoggers/#on-board-diagnostic-obd-hvac-can-defrosters) .
7. Start engine. The on board diagnostic function for A/C control head -E87- begins (address word "08"). See «READ MEASURING VALUE BLOCK (FUNCTION 08)»(/audi/a8/d2-1994-1999/remont/heated-glassdefoggers/#on-board-diagnostic-obd-hvac-can-defrosters__read-measuring-value-block-function-08) . Indicated on display
8. Press buttons -0- and -8- to select "Read Measuring Value Block" function 08. Indicated on display
9. Press -Q- button to confirm input. Indicated on display
10. Input display group number "01" (overview. See «READ MEASURING VALUE BLOCK (FUNCTION 08)»(/audi/a8/d2-1994-1999/remont/heated-glassdefoggers/#on-board-diagnostic-obd-hvac-can-defrosters__read-measuring-value-block-function-08) ).
11. Press -Q- button to confirm input. Indicated on display

Scheme 29

1. Display "0" in display field 1 shows the compressor switched on (there is no compressor cut-off condition).
2. Table of possible displays in display field 1. See «DISPLAY GROUP 001 - A/C COMPRESSOR CUT-OFF CONDITIONS, VOLTAGE FOR A/C CLUTCH -N25-, VOLTAGE TO TERMINAL 15 AND REQUIREMENT FOR RECIRCULATING AIR MODE/SENSOR FOR AIR QUALITY -G238»(/audi/a8/d2-1994-1999/remont/heated-glassdefoggers/#on-board-diagnostic-obd-hvac-can-defrosters__display-group-001-ac-compressor) .
3. The voltage for the A/C clutch -N25- is displayed in display field 2 (for example, 12.5 V).
4. Display field 3 shows the voltage to terminal 15 (for example, 12.5 V).
5. Display field 4 shows operating condition of the fresh/recirculating air. Table of possible displays in display field 4. See «DISPLAY GROUP 001 - A/C COMPRESSOR CUT-OFF CONDITIONS, VOLTAGE FOR A/C CLUTCH -N25-, VOLTAGE TO TERMINAL 15 AND REQUIREMENT FOR RECIRCULATING AIR MODE/SENSOR FOR AIR QUALITY -G238»(/audi/a8/d2-1994-1999/remont/heated-glassdefoggers/#on-board-diagnostic-obd-hvac-can-defrosters__display-group-001-ac-compressor) .

Scheme 30

Scheme 31

1. Read display from display field 4.
2. Specified values: "00" (no requirement for "recirculating air", A/C in fresh air mode with fresh air operation) or "60" ("Partial recirculating air," fresh air and recirculating air flap open)
3. Place spray head -A- of test bottle over air inlet of sensor for air quality -B-.
4. Activate spray head -C- of test bottle for 1 second.

Note. The content of the test gas bottle consists of pure oxygen with a specified amount of nitrogen oxide. The test gas for the air quality sensor is obtained as a replacement part under the number D007 855 A2. If the sensor comes in contact with cigarette smoke or gas from a lighter it will react.

1. Read display from display field 4. Specified value: "10" (requirement for "Automatic air recirculation" available, requirement is fulfilled, A/C switches to recirculating air mode)
2. Wait a short period of time (approx. 1 minute, depending on amount of test gas sprayed in sensor).
3. Read display field 4. Specified value: "00" (no requirement for "Recirculating air," A/C system in fresh air mode or "60" (partial recirculating air)

Note. In order to avoid quick shifting from the recirculating air/fresh air flap, the requirement from the sensor for "Automatic air recirculation mode" is at least 25 seconds (minimum duration period) especially if the pollutant concentration has been reduced considerably so that recirculating air mode is no longer necessary.

Scheme 32

Scheme 33

1. Operate switch for wiper/washer system until windshield washer pump -V5- has been cycled for approx. 2 seconds.
2. Read display from display field. Specified value: "30" (requirement for recirculating air due to washer/wiper system, A/C switches for approx. 10 seconds to the recirculating air mode)
3. Wait a short period of time.
4. Read display from display field 4. Specified Values: "00" (no requirement for "recirculating air, A/C in fresh air mode) or "60" (partial recirculating mode)

Note. Depending on the composition of the windshield washer fluid, the sensor can determine impurities in the air and request for "Automatic air recirculation." If when activating the wiper/washer system the mode does not switch over to recirculating air, check the wiring connection between A/C control head -E87- and wiper/washer intermittent relay -J31- according to the wiring diagram.

Scheme 34

1. Press --> button. Indicated on display
2. Push buttons -0- and -6- to select "End Output" function 06. Indicated on display
3. Press -Q- button to confirm input. Indicated on display
4. Switch ignition off and disconnect Data Link Connector (DLC).

Note. If the function of the sensor for air quality -G238- is OK for this test and there is a customer complaint continue as follows

1. Check dust and pollen filter for dirt.
2. Close DTC unit and select "Read Measuring Value Block" function 08.
3. Drive vehicle to area with relatively clean recirculating air (the system works in fresh air mode).
4. Now drive vehicle into an area with heavily polluted recirculating air (for example, on a street with construction or and truck traffic).

Display field 4, display group 001 must change from 00 or 60 to 10 when driving through a diesel exhaust cloud.

1. Read the notes. See «SENSOR FOR AIR QUALITY -G238-, FUNCTION»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__sensor-for-air-quality-g238-function) .