Restrictor, Reservoir and A/C Compressor Regulator Valve N280 (Externally Regulated Compressor), Checking

Restrictor, Reservoir And A/C Compressor Regulator Valve N280 (Externally Regulated Compressor), Checking

NOTE:
- Connect service station. Working With Service Station
- Observe test conditions. Pressures In Refrigerant Circuit, Checking (Using Service Station)

- Set engine speed to 2000 RPM.
- Observe pressure gauge of service station.

NOTE: Switching pressures for actuation of 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.
- Control current - B - is displayed in measured value block.
- High pressure is displayed in 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 regulating valve must be greater than 0.3 A in order to ensure reliable valve actuation.
- In the setting "maximum cooling output" control current is regulated to approx. 0.8 A (displayed in measured value block)
- At absolute pressure, 0 bar corresponds to absolute vacuum. Normal ambient pressure equals 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 in relation to this complaint, flush refrigerant circuit with compressed air and nitrogen.










NOTE:
- For the malfunction "high pressure normal, low pressure too low", note the following: If malfunctioning, evaporator may ice-up or 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.
- Check activation of A/C Compressor Regulator Valve N280







NOTE: Overfilling with refrigerant oil can occur if, for example, the compressor has been replaced without adjusting the quantity of refrigerant oil.