Pressure Checking, Vehicles With Restrictor and Reservoir With Internally Regulated Compressor

Pressure Checking, Vehicles With Restrictor And Reservoir 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.
- Connection with valve for low-pressure switch or at evaporator is only to be used for vehicles with no service connection on low pressure side and inaccessible connection at compressor or reservoir (measurement accuracy). Only applies to certain vehicles.

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 (measured at service connection) in bar
B - Low pressure (measured at connection with valve at compressor or reservoir) in bar
C - Permissible tolerance range
D - Low pressure (measured at connection with valve for low-pressure switch or at service connection) in bar
E - Permissible tolerance range







NOTE: If no fault is found in relation to this complaint, clean refrigerant circuit (flush using refrigerant R134a or blow through using compressed air and nitrogen).







NOTE:
- 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.
- 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.







NOTE:
- Pay attention to the following as regards fault "High pressure normal, low pressure too low" : This fault may cause the evaporator to ice up or the A/C Refrigerant Low Pressure Switch F73 to shut off the compressor although the amount of refrigerant in the circuit is OK.
- On the Audi 100, Audi A6 (up to and including Model Year 1997) and Audi V8, this fault may result in compressor being shut off by control head (if temperature at fresh-air blower drops below -3 degrees C.










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, drain compressor and replace reservoir. 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.