Pressure Checking, Vehicles With Expansion Valve and Receiver With Internally Regulated Compressor

Pressure Checking, Vehicles with Expansion Valve and Receiver with Internally Regulated Compressor

NOTE:
- Connecting A/C service station.
- Observe test conditions.

- Set engine speed to 2000 rpm.
- Observe pressure display (e.g. pressure gauge) of A/C service station.

NOTE:
- Switching pressures for refrigerant circuit switches are vehicle-specific.
- Pressures must be measured at service connections; component locations of these connections are vehicle-specific.

Specifications

High-pressure side:
Increasing from initial pressure (on connecting pressure gauges) to max. 20 bar

Low-pressure side:







Decreasing from initial pressure (on connecting pressure gauges) to value in graph
A - High pressure in bar
B - Low pressure in bar
C - Permissible tolerance range







NOTE: If no malfunction can be found and air conditioner operation is not OK when test is repeated, clean refrigerant circuit (flush using refrigerant R134a or blow through using compressed air and nitrogen).







NOTE: If operation is not OK after cleaning refrigerant circuit flushing with R134a or blowing through using compressed air and nitrogen), expansion valve must be replaced.







NOTE:
- It is not initially necessary to clean the refrigerant circuit (flush using refrigerant R134a or blow through using compressed air and nitrogen) when this problem occurs since normally, there is only a small quantity of moisture in the system which can be removed by lengthy evacuation.
- If problem involving moisture in refrigerant circuit only occurs after a lengthy operating period or only infrequently (low pressure drops below specification and evaporator ices up), it is sufficient to replace the dryer (adjust quantity of refrigerant oil). Refrigerant circuit is then to be evacuated for at least 3 hours.







NOTE: If air conditioner operation is not OK when test is repeated, re-install old expansion valve, clean refrigerant circuit (flush using refrigerant R134a or blow through using compressed air and nitrogen ). Then replace A/C compressor and receiver.










NOTE:
- If air conditioner operation is not OK when test is repeated, re-install old expansion valve, clean refrigerant circuit (flush using refrigerant R134a or blow through using compressed air and nitrogen). Then replace A/C compressor and receiver.
- With this fault, evaporator may ice up although quantity of refrigerant in circuit is OK.







NOTE:
- Overfilling with refrigerant oil can occur if, for example, the compressor has been replaced without adjusting the quantity of refrigerant oil.
- If there is too much refrigerant oil in the circuit, the compressor must be drained and the receiver must be replaced. After cleaning the refrigerant circuit (flushing with refrigerant R134a or blowing through using compressed air and nitrogen), the correct quantity of refrigerant oil is filled into the circuit.