Restrictor, Reservoir and A/C Compressor Regulator Valve, Checking

Restrictor, Reservoir And A/C Compressor Regulator Valve, Checking

NOTE:
- Connecting service station.
- Observe test requirements.

- Bring engine speed up to 2000 RPM.
- Observe pressure gauge of A/C service station.

NOTE: Switch pressures for activating the A/C Compressor Regulator Valve N280 and Coolant Fan V7 are vehicle-specific.

Specified Values

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

Low-Pressure Side:







Decreasing from initial pressure (on connecting pressure gauges) to value in graph.
A - Low pressure (measured at service connection) in bar absolute
B - Control current for A/C Compressor Regulator Valve N280.
C - Permissible tolerance range

NOTE:
- Under unfavorable conditions (very high ambient temperatures, high humidity), pressure on high-pressure side may increase to max. 29 bar.
- The control current - B - is shown in the measured value block.
- The high pressure is shown in the measured value block.
- Low pressure settles as a function of control current for A/C Compressor Regulator Valve N280 within compressor output range in tolerance range.
- Under unfavorable conditions (very high ambient temperatures, high humidity), compressor output may not always be sufficient to attain the specified value.
- The specified operating current for the regulator valve must be greater than 0.3 A in order to ensure reliable valve activation.
- In the setting "maximum cooling output" control current is regulated to approximately 0.8 A (displayed in measured value block).
- At absolute pressure, 0 bar corresponds to absolute vacuum. Normal ambient pressure corresponds to 1 bar absolute pressure. 0 pressure corresponds to an absolute pressure of one bar on most pressure gauges (indicated by - 1 bar below 0).







NOTE:
- If no malfunction is found with this complaint, flush (clean) refrigerant circuit with refrigerant R134a.
- If that is not possible in this workshop, flush refrigerant circuit with compressed air and remove moisture with nitrogen.







- For the malfunction "high pressure normal, low pressure too low", note the following: faulty, the evaporator can ice up or the cooling output is not reached.
- With this malfunction, evaporator may ice up although quantity of refrigerant in circuit is OK.
- Check measured values of Evaporator Vent Temperature Sensor G263 or Evaporator Temperature Sensor G308
- Check activation of A/C Compressor Regulator Valve N280.







- Overfilling with refrigerant oil can occur if, for example, the compressor has been replaced without adjusting the quantity of refrigerant oil.
- If the A/C compressor is not replaced, the refrigerant oil should be drained from the A/C compressor via the drain plug (replace O-ring). Out of the entire quantity of refrigerant oil, 50 grams should be put in the A/C compressor and the rest in the refrigerant circuit.