Troubleshooting Using Pressure Measurement (R 134a) - Refrigerant System

NOTE: Connect service station to car and open both valves on the charging hoses. Adjust air-conditioning system on the control unit in such a way as described for measuring air-conditioning efficiency.





High inlet and outlet pressures indicate an overcharged system, contaminated condenser or detective additional fan.

Remedy:
Draw out refrigerant, discharge and recharge system, clean condenser and check additional fan, replacing if necessary.





High inlet pressure and normal outlet pressure indicate a detective compressor.

Remedy:
Replace compressor.





Compressor does not run with equal inlet and outlet pressures.

Remedy:
Once the frost protection on the compressor has switched off, check evaporator sensor or power supply to coupling (refer to
Inspection Manual Electrics/Electronics HG 64). Otherwise check magnetic coupling mechanically (slips).





Low inlet pressure and normal outlet pressure indicate an insufficient charged volume or restricted low-pressure side of the system.

Remedy:
1. Check, whether evaporator has ice; then check evaporator sensor.
2. Draw out and measure refrigerant. If the drawn-out volume is approx. the same as specified charge volume check flow of expansion valve; then discharge and recharge the system.





Low inlet pressure and high outlet pressure indicate a restricted high pressure side.

Remedy:
Check condenser, drier and expansion valve.