A/C Refrigerant System (R-134a), Checking Pressures
Safety measures refer to "A/C System (R-134a), Safety Measures". Service Precautions
Before checking refrigerant system pressures, check A/C system cooling performance.
Use high pressure service valve for checking system pressures.
Test requirements
- Condenser and radiator clean and tree of obstructions (clean if necessary)
- Drive belts for compressor and generator in good condition and properly tensioned
- All air ducts, covers and seals OK and correctly installed
- Check DTC memory using VAG 1551 scan tool and eliminate/repair any malfunctions indicated (not affecting A/C system)
- All air distribution flaps reach end positions
- Engine at normal operating temperature
- Evaporator housing and heater box do not leak air (draw in secondary air) at high fresh air blower speed
- Outside (ambient) temperature must be between 15 - 45 °C (59 - 113 °F)
- Engine running and system set to maximum cooling (AUTO operating mode with LO temperature setting selected):
- Switch compressor on (warning light in ECON button does not light up)
- Temperature selection LO (for driver and passenger side)
If the compressor is activated (A/C clutch is switched on):
- Fresh air blower -V2- runs
- Coolant fan -V7- runs (at least in 1st speed)
- Airflow flap closes and fresh air/recirculated air flap opens (within 1 minute after starting vehicle)
NOTE: With fresh air/recirculated fed air flap open air flows out of outlets in the instrument panel even though the air flow flap is closed.
Preparation work
- Check DTC memory and determine and repair all possible malfunctions, refer to"On Board Diagnostic, Air Conditioning System".
Checking
- Switch ignition off.
- Connect high pressure hose of refrigerant recovery/recycling/recharging unit Kent-Moore ACR4, or equivalent, to high pressure service connection, refer to "Quick Coupling Connections".
- Leave low pressure hose of refrigerant recovery/recycling/recharging unit disconnected.
NOTE: Only the high pressure service valve is used for A/C system servicing. Perform all A/C system service operations (i.e. discharging, evacuating and charging) through the high pressure service valve only.
Outside (ambient ) Base pressure in refrigerant
temperature 1) 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) 5.6 bar (81.2 psi)
+30 °C (86 °F) 6.7 bar (97.2 psi)
+35 °C (95 °F) 7.8 bar (113.1 psi)
+40 °C (104 °F) 9.1 bar (132.0 psi)
+45 °C (113 °F) 10.5 bar (152.3 psi)
1) All components of A/C system must be at the specified temperature for an accurate pressure measurement.
If A/C refrigerant system base pressure is less than specified on chart, system is low on refrigerant:
- Check system for leaks using halogen leak detector Hitec H1400A-TEL or equivalent, repair system as necessary.
- Check pressure relief valve on A/C compressor.
If the pressure relief valve has blown:
- Check actuation of coolant fan -V7- according to wiring diagram.
- Check for pinched, kinked or damaged refrigerant lines/hoses.
If no problems are found:
- Discharge refrigerant system, then evacuate and recharge.
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. Compressor runs continuously.
NOTE: If A/C clutch -N25- is not engaged check voltage supply to A/C clutch according to wiring diagram. If voltage is OK, repair (replace) A/C clutch, refer to "A/C Clutch -N25-, Servicing (Denso Compressor)". Service and Repair
- Raise engine speed to 2000 RPM.
- Note pressure on A/C high pressure gauge.
Specified high pressure value: high side (discharge) pressure increases from base pressure (engine OFF) to maximum 20 bar (290 psi).
NOTE: Switching pressure specifications of A/C refrigerant pressure switch -F129-, refer to "A/C Pressure Switch -F129-, Functions".
Pressure in A/C system corresponds to chart or is higher:
- Start engine.
- Adjust A/C to maximum cooling performance.
NOTE: If compressor is not activated, note test requirements.