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AC electrical check
Checking in vehicles with an operating and display unit with one display
List of envisaged electrical checks (at operating and display unit -E87)
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Test step
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Component tested
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Page
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1
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- Power supply, earth connection and illumination of operating and display unit -E87.
Signal for ignition off time
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01-163
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2
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- Temperature sensors/senders (-G17, -G56, -G89, -G192).
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01-168
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3
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- Fresh air blower with corresponding control unit (-V2, -J126).
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01-172
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4
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- Positioning motors for air conditioner and corresponding potentiometers
(-V68/-G92, -V70/-G112, -V71/-G113, -V85/-G114).
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01-174
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5
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- Pressure signal from radiator fan control unit -J293.
"Air conditioner compressor cut-in" output
Signal "Engine temperature too high".
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01-177
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6
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- Actuation of air conditioner magnetic clutch -N25.
Actuation of radiator fan -V7
Actuation of two-way valve for refrigerant shut-off valve -N147
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01-182
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Test step 1
Voltage supply, earth connection, illumination of the operating and display unit -E87 and signal for "ignition off time" (standing time)
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Select measuring range on hand-held multimeter V.A.G 1526:
Voltage measurement (20V =)
- Adapter cable V.A.G 1598/12 connected
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Test step
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V.A.G 1598 socket
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Testing of
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▪ Test conditions
- Additional operations
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Specified value
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Remedies if specified value not attained
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1.1
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15
and
14
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Terminal 15 and earth connection on -E87
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▪ Ignition on.
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- Approx. battery voltage
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- Use current flow diagram to repair power supply and/or earth connection.
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1.2
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15
and
13
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Earth connection at the -E87
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▪ Ignition on.
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- Approx. battery voltage
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- Use current flow diagram to repair earth connection.
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Select measuring range on hand-held multimeter V.A.G 1526:
Voltage measurement (20V =)
- Adapter cable V.A.G 1598/12 connected
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Test step
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V.A.G 1598 socket
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Testing of
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▪ Test conditions
- Additional operations
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Specified value
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Remedies if specified value not attained
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1.3
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12
and
14
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Terminal 58 on -E87
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▪ Ignition on.
▪ Switch side lights on
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- Approx. battery voltage
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- Use current flow diagram to repair power supply.
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1.4
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12
and
14
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Terminal 58 on -E87
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▪ Ignition on.
▪ Side lights off
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- less than 2 V
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- Use the current flow diagram to rectify short to positive.
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Select measuring range on hand-held multimeter V.A.G 1526:
Voltage measurement (20V =)
- Adapter cable V.A.G 1598/11 connected
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Test step
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V.A.G 1598 socket
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Testing of
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▪ Test conditions
- Additional operations
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Specified value
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Remedies if specified value not attained
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1.5
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10 and
earth
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Terminal 58d on -E87
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▪ Ignition on.
▪ Side lights on
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- 0 to 12 V (regardless of the illumination control setting).
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- Use current flow diagram to locate and eliminate open circuit or short circuit
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1.6
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10 and
earth
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Terminal 58d on -E87
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▪ Ignition on.
▪ Side lights off
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- 0 to 12 V (regardless of the illumination control setting).
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- Use current flow diagram to locate and eliminate open circuit or short circuit
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Notes:
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◆ Earth applied e.g. to connector D contact 14.
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◆ The brightness of the display of the -E87 is controlled via terminal 58d.
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◆ The voltage at terminal 58d is generated as a square-wave signal by the dash panel insert. The brightness of -E87 displays is determined by the actuation time. The measuring instrument displays the average value.
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◆ The actuation time at terminal 58d is governed by the illumination control setting and the brightness level determined by the photosensor in the dash panel insert.
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Select measuring range on hand-held multimeter V.A.G 1526:
Voltage measurement (20V =)
- Adapter cable V.A.G 1598/11 connected
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Test step
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V.A.G 1598 socket
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Testing of
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▪ Test conditions
- Additional operations
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Specified value
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Remedies if specified value not attained
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1.7
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11 and
earth
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Terminal 58s on -E87
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▪ Ignition on.
▪ Side lights switched on.
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- 0 to 12 V
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- Use current flow diagram to locate and eliminate open circuit or short circuit
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1.8
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11 and
earth
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Terminal 58s on -E87
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▪ Ignition on.
▪ Side lights off
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- approx. 0 V.
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- Use the current flow diagram to locate and rectify short to positive
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Notes:
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◆ Earth applied e.g. to connector D contact 14.
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◆ The brightness of the display of the -E87 is controlled via terminal 58s.
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◆ The voltage at terminal 58s is governed by the setting of the illumination control.
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Voltage tester V.A.G 1527,
- Adapter cable V.A.G 1598/11 connected
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Test step
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V.A.G 1598 socket
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Testing of
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▪ Test conditions
- Additional operations
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Specified value
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Remedies if specified value not attained
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1.9
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12
and earth
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Signal for ignition off time
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▪ Ignition on.
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- the LED illuminates in voltage tester
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- Use current flow diagram to locate and eliminate open circuit or short circuit
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1.10
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12
and earth
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Signal for ignition off time
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▪ Ignition on.
Start engine.
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- the LED illuminates in voltage tester
when the engine is started, the LED in the voltage tester flickers briefly (time signal) and remains illuminated
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- Use current flow diagram to locate and eliminate open circuit or short circuit
Check dash panel insert
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Note:
Earth applied e.g. to connector D contact 14.
Test step 2
Temperature sensor/sender
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Select measuring range on hand-held multimeter V.A.G 1526:
Resistance measurement (20 kω)
- Adapter cable V.A.G 1598/11 connected
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Test step
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V.A.G 1598 socket
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Testing of
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▪ Test conditions
- Additional operations
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Specified value
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Remedies if specified value not attained
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2.1
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32
and
25
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Footwell vent temperature sender -G192
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- Measure temperature at sender fitting location.
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- Governed by the temperature at the sensor/pickup fitting location
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- Use current flow diagram to locate and eliminate short circuit, open circuit or contact resistance.
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2.2
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31
and
25
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Centre vent temperature sender -G191
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▪ Vehicles with map-controlled cooling
Measure temperature at sender fitting location.
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=> Table, Page 01-171.
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- Replace temperature sensor/sender.
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Contact in connector B contact 11 for short circuit
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▪ Vehicles without map-controlled cooling
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- ∞ω
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- Find short to connector B contact 11 according to current flow diagram and eliminate.
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Note:
Centre vent temperature sender -G191 is only installed in vehicles with map-controlled cooling.
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Select measuring range on hand-held multimeter V.A.G 1526:
Resistance measurement (20 kω)
- Adapter cable V.A.G 1598/11 connected
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Test step
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V.A.G 1598 socket
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Testing of
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▪ Test conditions
- Additional operations
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Specified value
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Remedies if specified value not attained
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2.3
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33
and
25
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Temperature sensor for fresh air intake duct -G89
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- Measure temperature at the sensor fitting location.
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- Dependent on the temperature at the sensor fitting location => Table, Page 01-171.
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- Use current flow diagram to locate and eliminate short circuit, open circuit or contact resistance.
Replace temperature sensor.
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Select measuring range on hand-held multimeter V.A.G 1526:
Resistance measurement (20 kω)
- Adapter cable V.A.G 1598/12 connected
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Test step
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V.A.G 1598 socket
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Testing of
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▪ Test conditions
- Additional operations
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Specified value
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Remedies if specified value not attained
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2.4
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8
and
2
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Ambient temperature sensor -G17
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- Measure temperature at the sensor fitting location.
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- Dependent on the temperature at the sensor fitting location => Table, Page 01-171.
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- Use current flow diagram to locate and eliminate short circuit, open circuit or contact resistance.
Replace temperature sensor.
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Ambient temperature-dependent resistance of temperature sensors/senders in kω(kilo-ohms)
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At sensor/sender installation location, temperature measured in °C
(degrees Celsius)
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Sender
-G192
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Temperature sensor
-G17
-G89
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Sender
-G191
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-30
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(52.7)
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18.1
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-
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-20
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(28.6)
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9.95
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-
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-10
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16.2
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5.59
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(47)
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0
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9.40
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3.28
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(29)
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5
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7.27
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2.54
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(23)
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10
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5.66
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1.99
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18.5
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15
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4.45
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1.57
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15
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20
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3.50
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1.25
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12.2
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25
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2.79
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1.00
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10.0
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30
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2.23
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0.80
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8.3
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35
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1.80
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0.65
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6.8
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40
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1.45
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0.53
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5.7
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50
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0.97
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0.36
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4.1
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60
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0.67
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0.25
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2.9
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70
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0.47
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-
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2.2
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Test step 3
Fresh air blower -V2 and relevant control unit -J216
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Select measuring range on hand-held multimeter V.A.G 1526:
Voltage measurement (20V =)
- Adapter cable V.A.G 1598/11 connected
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Test step
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V.A.G 1598 socket
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Testing of
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▪ Test conditions
- Additional operations
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Specified value
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Remedies if specified value not attained
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3.1
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16
and
earth
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Control unit -J126
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▪ Ignition on.
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- Voltage less than 5 V.
Fresh air blower not running.
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- Use current flow diagram to locate and eliminate short to positive in the wiring between -J126 and -E87.
Replace control unit -J126.
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3.2
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4
and
earth
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Power supply for fresh air blower -V2
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▪ Ignition on.
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- approx. battery voltage
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- Use current flow diagram to repair power supply.
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Note:
Earth applied e.g. to connector D contact 14.
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Voltage tester V.A.G 1527,
- Adapter cable V.A.G 1598/11 connected
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Test step
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V.A.G 1598 socket
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Testing of
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▪ Test conditions
- Additional operations
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Specified value
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Remedies if specified value not attained
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3.3
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3
and
earth
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Power supply for control unit -J126 (via fresh air blower -V2)
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▪ Ignition on.
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- approx. battery voltage
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- Use current flow diagram to repair power supply.
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3.4
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4
and
16
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Control unit -J126
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▪ Ignition on.
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- LED in voltage tester lights up.
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- Use current flow diagram to locate and eliminate open circuit in the wiring between -J126 and -E87.
Find open circuit in earth wiring to -J126 and eliminate.
Check freedom of movement of fresh air blower -V2.
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- Fresh air blower is running
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- Replace control unit -J126.
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Note:
Earth applied e.g. to connector D contact 14.
Test step 4
Positioning motors for air conditioner and associated potentiometers
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Select measuring range on hand-held multimeter V.A.G 1526:
Resistance measurement (20 kω)
- Adapter cable V.A.G 1598/11 connected
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Test step
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V.A.G 1598 socket
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Testing of
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▪ Test conditions
- Additional operations
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Specified value
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Remedies if specified value not attained
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4.1
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25
and
36 /
37 /
38 /
39
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Potentiometer (in the positioning motor)
-G 92 (-V 68)
-G114 (-V85)
-G112 (-V70)
-G113 (-V71)
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- Greater than 0.1 kωand less than 5.7kω ((depending on the setting of the positioning motor)
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- Use current flow diagram to locate and eliminate open circuit, contact resistance or short circuit
Replace positioning motor
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4.2
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34
and
36 /
37 /
38 /
39
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Potentiometer (in the positioning motor)
-G 92 (-V 68)
-G114 (-V85)
-G112 (-V70)
-G113 (-V71)
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- Greater than 0.1 kωand less than 5.7kω ((depending on the setting of the positioning motor)
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- Use current flow diagram to locate and eliminate open circuit, contact resistance or short circuit
Replace positioning motor
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Notes:
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◆ The resistance of potentiometers in the positioning motors (specified value: 3.6 kωto 5.7 kω between contact 1 and 3) can only be measured directly on the positioning motor (parallel connection).
-
◆ The resistance of the potentiometers in the positioning motors (between contacts 1 and 2, as well as contacts 3 and 2) is governed by the setting of the positioning motor, it must only be measured with the positioning motorfitted. The maximum specified value will not be obtained in test steps 4.1 and 4.2. (To obtain the maximum specified value, all connectors on the other positioning motor would have to be detached during the measurement; the motors are connected in parallel).
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◆ If -E87 detects the fault "potentiometer short to earth or open circuit/short to positive", check all the potentiometers (in the 4 positioning motors) and the corresponding wiring.
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◆ On vehicles with right-hand drive, connections 1 and 2 as well as 4 and 6 on the positioning motor are reversed (check part number and current flow diagram).
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Select measuring range on hand-held multimeter V.A.G 1526:
Resistance measurement (200 ω)
- Adapter cable V.A.G 1598/11 connected
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Test step
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V.A.G 1598 socket
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Testing of
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▪ Test conditions
- Additional operations
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Specified value
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Remedies if specified value not attained
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4.3
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21
and
22
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Temperature flap positioning motor -V68
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- 20 ωto 100ω.
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- Use current flow diagram to locate and eliminate open circuit, contact resistance or short circuit
Replace positioning motor
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Select measuring range on hand-held multimeter V.A.G 1526:
Resistance measurement (200 ω)
- Adapter cable V.A.G 1598/11 connected
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Test step
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V.A.G 1598 socket
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Testing of
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▪ Test conditions
- Additional operations
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Specified value
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Remedies if specified value not attained
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4.4
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26
and
27
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Central flap positioning motor -V70
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- 20 ωto 100ω.
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- Use current flow diagram to locate and eliminate open circuit, contact resistance or short circuit
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4.5
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28
and
29
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Air flow flap positioning motor -V71
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- 20 ωto 100ω.
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- Replace positioning motor
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4.6
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23
and
24
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Footwell/defroster flap positioning motor -V85
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- 20 ωto 100ω.
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Test step 5
Pressure signal from radiator control unit for refrigerant -J293, output "air conditioner compressor cut-in", signal "engine temperature too high"
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Select measuring range on hand-held multimeter V.A.G 1526:
Voltage measurement (20V =)
- Adapter cable V.A.G 1598/12 connected
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Test step
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V.A.G 1598 socket
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Testing of
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▪ Test conditions
- Additional operations
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Specified value
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Remedies if specified value not attained
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5.1
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7
and
14
|
Signal from radiator fan control unit -J293.
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▪ Ignition on.
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- approx. battery voltage
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- Use current flow diagram to locate and eliminate open circuit or contact resistance.
Check high-pressure sensor ().
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Notes:
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◆ Depending on high-pressure sensor -G65 signal, radiator fan control unit -J293:
- indicates to operating and display unit -E87 that the refrigerant circuit pressure is OK and the compressor
can be switched on (via magnetic clutch -N25).
- switches radiator fan to 2nd speed if pressure increases.
-
◆ If code 1 "pressure switch -F129 open" is displayed in measured value block 1 as a compressor shutoff criterion:
- Use current flow diagram to check the wiring to -G65 for a loose contact.
- Use current flow diagram to check wiring between control unit -J293 and -E87 for loose contact.
- Check the actuation of the radiator fan -V7 speed 1 (=>Final control diagnosis, Page 01-51).
- Check signal from high-pressure sensor -G65 .
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Voltage tester V.A.G 1527,
Operating and display unit connected to the test box (adapter cable V.A.G 1598/11 and /12)
- Adapter cable V.A.G 1598/11 connected
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Test step
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V.A.G 1598 socket
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Testing of
|
▪ Test conditions
- Additional operations
|
Specified value
|
Remedies if specified value not attained
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5.2
|
Earth
and
6
|
Signal "Engine temperature too high"
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▪ Engine running
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▪ LED in the voltage tester flickers briefly.
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- Use the current flow diagram to locate and rectify short to earth.
Rectify the air conditioner compressor shutoff condition in the dash panel insert.
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Notes:
-
◆ Earth applied e.g. to connector D contact 14.
-
◆ Brief flickering of the LED in the voltage tester indicates that the dash panel insert is transmitting a temperature signal.
-
◆ The assignment of the ignition key is transmitted to the -E87 through the dash panel insert together with the refrigerant temperature and the signal "engine temperature too high" when ignition is switched on (data telegram). If the refrigerant temperature is too high, no information may be transmitted.
-
◆ The assignment of the ignition key can only be recognised and therefore transmitted by the dash panel insert on vehicles fitted with an immobiliser.
-
◆ When the ignition is switched on, the -E87 starts with the setting which was valid the last time the ignition was switched off with this key (temperature, air distribution, fresh air blower speed).
-
◆ The signal from the dash panel insert (data telegram) cannot be checked with workshop tools.
=> Electrical System; Repair group 90; Repair dash panel insert
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Voltage tester V.A.G 1527,
Operating and display unit connected to the test box (adapter cable V.A.G 1598/11 and /12)
- Adapter cable V.A.G 1598/11 connected
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Test step
|
V.A.G 1598 socket
|
Testing of
|
▪ Test conditions
- Additional operations
|
Specified value
|
Remedies if specified value not attained
|
|
5.3
|
4
and
1
|
"Air conditioner compressor cut-in" output
|
▪ Engine running
▪ Compressor off (lamp in ECON button of -E87 lights up).
Switch on compressor.
|
- LED in voltage tester lights up.
LED in voltage tester lights up a little less brightly.
|
- Use current flow diagram to locate and eliminate open circuit or short circuit.
Rectify AC compressor shutoff condition in the engine control (emergency operation).
Use the current flow diagram to locate and rectify short to earth.
|
|
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|---|
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Select measuring range on hand-held multimeter V.A.G 1526:
Current measurement (200 mA =)
Operating and display unit connected to the test box (adapter cable V.A.G 1598/11 and /12)
- Adapter cable V.A,G 1598/11 connected.
|
|
Test step
|
V.A.G 1598 socket
|
Testing of
|
▪ Test conditions
- Additional operations
|
Specified value
|
Remedies if specified value not attained
|
|
5.4
|
Earth
and
1
|
"Air conditioner compressor cut-in" output
|
▪ Engine running
▪ Compressor switched off.
Switch on compressor.
|
- Less than 5 mA
Less than 50 mA
Compressor is not switched on.
|
- Use current flow diagram to locate and eliminate short circuit.
Check actuation of control unit -J293 ().
Renew operating and display unit -E87.
|
Note:
Earth applied e.g. to connector D contact 14.
Test step 6
Radiator fan actuation -V7, magnetic clutch actuation -N25
|
|
|---|
|
Select measuring range on hand-held multimeter V.A.G 1526:
Current measurement (20 A =)
- Adapter cable V.A.G 1598/12 connected
|
|
Test step
|
V.A.G 1598 socket
|
Testing of
|
▪ Test conditions
- Additional operations
|
Specified value
|
Remedies if specified value not attained
|
|
6.1
|
15
and
4
|
Actuation of radiator fan -V7
|
▪ Engine running
|
- Less than 1 A
Radiator fan -V7 running at speed 1 (observe relevant notes)
|
- Use current flow diagram to locate and eliminate open circuit or short to positive or earth in the wiring between -J293 and -E87.
Check actuation of control unit -J293 ().
Control unit -J293 defective - replace.
|
|
|
|
|
|
|
|
|
|
(cont.)
▼
|
|
|
|---|
|
Select measuring range on hand-held multimeter V.A.G 1526:
Current measurement (20 A =)
- Adapter cable V.A.G 1598/11 connected
|
|
Test step
|
V.A.G 1598 socket
|
Testing of
|
▪ Test conditions
- Additional operations
|
Specified value
|
Remedies if specified value not attained
|
|
6.1
(cont.)
|
(15
and
4)
|
Actuation of air conditioner magnetic clutch -N25
|
▪ Engine running
|
- Compressor is driven.
|
- Use current flow diagram to locate and eliminate open circuit or short to positive or earth in the wiring between -E87 and -J293.
Check actuation of control unit -J293 ().
Control unit -J293 defective - replace.
|
Notes:
-
◆ Control unit -J293, installed in vehicles with high-pressure sensor -G65, is available in 2 designs.
- In design "1" the radiator fan is automatically switched on in conjunction with the compressor (the first fan speed
is activated regardless of the pressure in the refrigerant circuit).
- In design "2" the compressor is switched on without actuation of the radiator fan; the first
fan speed is only activated once the pressure in the refrigerant circuit exceeds 12 bar.
-
◆ In vehicles with map-controlled cooling the radiators are controlled by the engine control unit dependent on the refrigerant temperature.
=> Relevant Workshop Manual Injection and Ignition system
|
|
|---|
|
Select measuring range on hand-held multimeter V.A.G 1526:
Current measurement (20 A =)
- Adapter cable V.A.G 1598/12 connected
|
|
Test step
|
V.A.G 1598 socket
|
Testing of
|
▪ Test conditions
- Additional operations
|
Specified value
|
Remedies if specified value not attained
|
|
6.2
|
4
and
6
|
Actuation of two-way valve for refrigerant shut-off valve -N147
|
▪ Engine running
|
- lower than 1 A (observe notes)
|
- Use current flow diagram to locate and eliminate open circuit or short to positive or earth in the wiring between -J293 and -E87.
Defective twoway valve, replace.
|
|
|
|
|
|
- the refrigerant shut-off valve closes (observe notes)
|
- Check vacuum pressure supply via two-way valve -N147 to refrigerant shut-off valve ()
Defective twoway valve, replace.
Refrigerant shut-off valvedefective, replace.
|
Notes:
-
◆ The "two-way valve -N147" and the refrigerant shut-off valve is only installed into vehicles with map-controlled engine cooling.
-
◆ The refrigerant through flow through the heat exchanger of the air conditioner unit is blocked via the refrigerant shut-off valve by the operating and display unit -E87.
|
