Automatic A/C
Test conditions- Condenser and radiator clean and free of obstructions (clean if necessary)
- Ribbed belt in good condition and properly tensioned
- All air ducts, covers and seals OK and correctly installed
- Car not parked in direct sunlight
- Engine at normal operating temperature
- Coupling between evaporator housing and heater box tight and does not draw secondary air (at high fresh air blower speed)
- With engine running, system in "Auto" operating mode with "LO" temperature setting selected, instrument panel air outlets open, recirculation button pressed (recirculating air symbol lights up in display) and compressor switched ON (compressor symbol "ice crystal" lights up in display)
- Coolant fan runs.
- Fresh air blower runs at highest speed.
- Recirculating/fresh air flap in "recirculating air" position.
- Air flows from instrument panel air outlets
- Coolant shutoff valve closed
- Temperature flap in "cooling" position
- Compressor runs (compressor clutch engaged)
NOTE: If one or more of the specified results does not occur, check Diagnostic Trouble Code (DTC) memory and perform output Diagnostic Test Mode (DTM)
Preparations
- Check DTC memory using VAG 1551 scan tool, and eliminate/repair any malfunctions.
- Perform basic setting.
- Close hood, doors, windows and sunroof.
- Measure outside (ambient) temperature.
Checking
Outlet air temperature from center instrument panel vent must lie within tolerance range after A/C has run for 5 minutes.
A - Outlet air temperature from center instrument panel vent
B - Outside (ambient) temperature
C - Permissible tolerance range
- Switch ignition ON.
- Press "Auto" button to set A/C control head to "Auto" operating mode.
- Press "-" (minus) temperature select button until "LO" temperature setting is displayed.
NOTE: Do not select blower speed or press any air distribution buttons.
- Open all instrument panel air vents.
- Start engine.
Compressor ON "ice crystal" symbol in left display sector of A/C control head lights up.
- Increase engine speed to 2000 RPM (start time measurement).
- Measure outlet air temperature from center instrument panel vent.
- Compare temperature readings with chart at left after A/C has run for 5 minutes.
- Temperature must be within tolerance range
If specified values are NOT obtained:
- Check DTC memory using VAG 1551 scan tool and repair/ eliminate any malfunctions.
- Erase DTC memory (function 05).
- End output (function 06), but leave VAG 1551 connected.
- Repeat A/C system cooling performance test.
If A/C compressor switches OFF during test:
- On VAG 1551 scan tool, immediately insert "AC/Heating Electronics" address word 08, select "Read Measuring Value Block" function 08, and press -Q- button to confirm input.
- Input display group number 001 (compressor switch-off conditions).
- Read display group 001, display field 1, and repair/eliminate cause of A/C compressor switch-off.
Compressor switch-off condition - code "2"
- End output.
- Remove A/C refrigerant high pressure switch -F118- and reconnect to connector.
- Connect A/C high pressure gauge to service valve.
- Repeat A/C system cooling performance test and watch gauge.
Specified values
- High side (discharge) pressure increases from base pressure (engine OFF) to maximum 20 bar (290 psi)
- A/C refrigerant high pressure switch -F23- switches coolant fan (V7) to second speed operation between 13.1 - 17.5 bar (190.0 - 254.0 psi) gauge pressure.
If NO:
- Check triggering of coolant fan according to wiring diagram, repair as necessary.
If specified high side system pressure is exceeded:
- See A/C refrigerant system, troubleshooting. Testing and Inspection
If A/C compressor clutch does not engage:
- Check wiring between A/C control head -F87- and high pressure switch -F118- for open circuit or loose connection according to wiring diagram, repair as necessary.
If required cooling performance is attained and no malfunction is determined:
- Replace A/C refrigerant high pressure switch -F118-.
Compressor switch-off condition - code "3"
- End output.
- Remove A/C refrigerant low pressure switch -F73- and bridge connector terminals.
- Connect A/C low pressure gauge to service valve.
- Repeat A/C system cooling performance test and watch gauge.
Specified values
Low side (suction) pressure decreases from base pressure (engine OFF) to pressure value
A - Outside (ambient) temperature
B - Low side (suction) pressure
C - Low side (suction) pressure specified value with low pressure gauge connected to service valve on compressor
D - Low side (suction) pressure specified value with low pressure gauge connected to service valve for low pressure switch -F73-
- Compare actual low side (suction) pressure with chart.
- Permissible deviation between actual and specified values: ± 0.2 bar (3 psi)
