Refrigerant System

Before checking system pressures, read and follow test conditions. Testing and Inspection
- Switch ignition OFF.
- Remove low pressure switch -F73- and bridge connector terminals.
- Remove high pressure switch -F118- and reconnect connector to switch.
- Connect A/C manifold gauge set to service valves. Service valves located below switches -F73- and -F118-
- Read gauge pressures (high and low).


Outside (ambient) Base pressure in refrigerant
temperature system (engine OFF)
+ 15 °C ( 59 °F) 3.9 bar ( 56.5 psi)
+ 20 °C ( 68 °F) 4.7 bar ( 68.2 psi)
+ 25 °C ( 77 °F) 5.5 bar ( 79.8 psi)
+ 30 °C ( 86 °F) 6.6 bar ( 95.7 psi)
+ 35 °C ( 95 °F) 7.5 bar (108.8 psi)
+ 40 °C (104 °F) 8.8 bar (127.6 psi)
+ 45 °C (113 °F) 9.8 bar (142.1 psi)

If A/C refrigerant system base pressure is less than specified on chart, system is low on charge:
- Check system for leaks using a leak detector, repair as necessary.
- Check pressure relief valve on A/C compressor.

If the pressure relief valve has blown:
- Check triggering of coolant fan according to wiring diagram.
- Check for pinched or kinked refrigerant lines/hoses.
- Check refrigerant lines/hoses for visible damage.
If no problems are found:
- Discharge, evacuate and recharge A/C system.

If A/C refrigerant system pressure corresponds to or is higher than base pressure specified on chart:
- Start engine.
- Adjust A/C to maximum cooling.
A/C compressor clutch engages and compressor is driven
If A/C compressor is not driven:
- Check Diagnostic Trouble Code (DTC) memory using VAG 1551 scan tool and check voltage supply to A/C clutch -N25- according to wiring diagram.

If voltage to compressor clutch is OK:
- Repair (replace) A/C clutch.
- Raise engine speed to 2000 RPM.
- Make note of pressures on A/C pressure gauges.

Specified values
- High side (discharge) pressure increases from base pressure (engine OFF) to maximum 20 bar (290 psi)
- Low side (suction) pressure decreases from base pressure (engine OFF) to pressure value.





- A/C refrigerant high pressure switch -F23- switches coolant fan -V7- to second speed between 13.1 - 17.5 bar (190.0 - 254.0 psi) gauge pressure.

If coolant fan -V7- does not run at second speed:
- Check triggering of coolant fan according to wiring diagram, repair as necessary.
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)


NOTE: For switching pressure specifications of the A/C refrigerant low pressure switch -F73- , and A/C refrigerant high pressure switch -F118-.