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 are OK and correctly installed
- Car not parked in direct sunlight
- Engine at normal operating temperature
- Evaporator housing and heater box do 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 comes on in display) and compressor switched on (compressor symbol "ice crystal" comes on 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
- 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) Automatic Climate Control (Via Scan Tool)
- Check signal using output Diagnostic Test Mode (DTM) Output Diagnosis Test Mode (Function 03)
Preparation:
- Using VAG1551 scan tool, check DTC memory and eliminate/repair any malfunctions. Checking and Erasing DTC Memory
- Initiate "Basic Setting" function 04. Basic Setting (Function 04)
- Close hood.
- Measure outside (ambient) temperature.
- Close doors and windows.
Checking:
Outlet air temperature from center instrument panel vent must lie within tolerance range of Image 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.
- 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 comes on
- Increase engine speed (RPM) to 2000 and 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:
Did A/C Compressor switch off during cooling performance test?
Yes, Skip to "If A/C Compressor Switches Off During Test, below.
No, Continue.
- Using VAG1551 scan tool, check DTC memory and eliminate/repair any malfunctions. Checking and Erasing DTC Memory
- Erase DTC memory.
- End rapid data transfer but leave VAG1551 connected.
- Repeat A/C system cooling performance test.
- Also, Troubleshooting System
If A/C Compressor Switches Off During Test:
- Immediately enter address word 08 "Read measuring value block" into VAG1551 and press 0 button to confirm input.
- Enter display group number 001 for "Compressor switch-off conditions."
- Read display field 1 and repair/eliminate cause of A/C compressor switch-off. Read Measuring Value Block (Function 08)
Compressor Switch-Off Condition-Code "2":
- End rapid data transfer.
- Remove A/C refrigerant high pressure switch -F118- and reconnect to connector.
- Connect A/C high pressure gauge to service valve.
- Repeat A/C cooling performance test, and check A/C system pressures.
If coolant fan does not run at second speed:
- Check triggering of coolant fan according to wiring diagrams and repair as necessary.
If specified high side system pressure is exceeded Troubleshooting System
If A/C clutch does not engage:
- Check wiring between A/C control head -E87- and high pressure switch -F118- for open circuit or loose connection according to wiring diagrams and repair as necessary.
If required cooling performance is attained and no malfunction is determined:
- Replace high pressure switch -F118-.
Compressor Switch-Off Condition-Code "3":
- End rapid data transfer.
- Remove A/C refrigerant low pressure switch -F73- and bridge connector terminals.
- Connect A/C low pressure gauge to service valve.
- Repeat A/C cooling performance test, and check A/C system pressures. Refrigerant System
For additional codes, Read Measuring Value Block (Function 08)