Test sequence
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‒ Read measured value block, Display group 002, engine idling=>Page01-126.
→ Display on VAS 5051:
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‒ Check display in display zone -3-.
Note:
Display value "X" can be ignored during test procedure.
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‒ Switch on air conditioner, press the "Auto" key and select the lowest temperature.
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‒ Press the ◂ button to exit from the function "08 - Read data block".
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‒ Select diagnosis function "06 - End output".
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‒ Switch off ignition.
If the specification is not obtained:
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‒ Connect test box V.A.G 1598/31 to wiring harness for engine control unit.Do notconnect to the engine control unit itself:
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‒ Connecting test box to engine control unit without protective housing=>Page 23-49.
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‒ Connecting test box to engine control unit with protective housing=>Page 23-51.
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‒ Test for open circuit and short to positive or earth in the following wiring connection:
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Test box V.A.G 1598/31 Socket
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AC operating and display unit -E87 Contact
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34
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=> Current flow diagrams, Electrical fault-finding and Fitting locations binder
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‒ Rectify any open/short circuit as necessary.
Testing AC compressor shut-off
The engine control unit will shut off the air conditioner compressor in the following cases:
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◆ Heavy acceleration from low speeds (control unit detects angle change at accelerator position sender -G79 and receives road speed signal)
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◆ In the emergency programme (emergency running mode)
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◆ If the coolant temperature rises above 120 °C
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◆ For about 6 seconds after every engine start
Test sequence
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‒ Switch on air conditioning system.
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‒ Select the function "Final control diagnosis" and activate air conditioner compressor shut-off=>Page01-64.
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◆ The air conditioning compressor should shut off within 5 seconds (check visually) and then every 5 seconds cut in and shut off again.
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‒ Press the ◂button to exit from function "03 - Final control diagnosis".
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‒ Select diagnosis function "06 - End output".
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‒ Switch off ignition.
If the conditioner compressor is not switched off:
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‒ Connect test box V.A.G 1598/31 to wiring harness for engine control unit.Do notconnect to the engine control unit itself:
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‒ Connecting test box to engine control unit without protective housing=>Page 23-49.
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‒ Connecting test box to engine control unit with protective housing=>Page 23-51.
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‒ Test for open circuit and short to positive or earth in the following wiring connection:
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Test box V.A.G 1598/31 Socket
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AC operating and display unit -E87 Contact
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29
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=> Current flow diagrams, Electrical fault-finding and Fitting locations binder
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‒ Rectify any open/short circuit as necessary.
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