Manual A/C
Test conditions- Condenser and radiator clean and free of obstructions (clean if necessary)
- Ribbed drive 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; does not draw secondary air (at high fresh air blower speed)
- With engine running, A/C compressor switch ON and Recirculation button pressed, both indicator lights in A/C switch illuminate
- A/C compressor driven or switches ON
- Fresh air blower runs
- Coolant fan runs
- Recirculating/fresh air flap in "recirculating air" position.
- With engine running and temperature knob in "Max. cold" position, coolant shutoff valve (for heater) closed
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
- Close hood.
- Measure outside (ambient) temperature.
- Close doors, windows and sunroof.
- Switch ignition ON.
- Press A/C compressor switch and Recirculating button ON (both indicator lights illuminate).
- Set temperature control knob to max. cold position.
- Open all instrument panel air outlets.
- Switch fresh air blower to high speed (position 4).
- Set air distribution knob so that air flows from instrument panel vents.
- Start engine (start time measurement).
- Increase engine speed to 2000 RPM.
- 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 readings are not obtained:
- Remove A/C refrigerant low pressure switch -F73- and bridge connector terminals.
- Remove A/C refrigerant high pressure switch -F118- and reconnect to connector.
- Connect A/C manifold gauge set to high and low pressure service valves.
- Start engine.
- Connect VAG 1551 scan tool to Data Link Connectors (DLC) and select "Read Measuring Value Block" function 08.
- Perform A/C cooling performance test again, check system pressures and read display group 001, display field 1 on VAG 1551 display.
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 - 254 psi) gauge pressure.
If NOT:
- Check triggering of coolant fan according to wiring diagram, repair as necessary.
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)
