Expansion Valve, Receiver and A/C Compressor Regulator Valve N280 (With Externally Regulated Compressor)

Pressures For Vehicles With Expansion Valve, Receiver And A/C Compressor Regulator Valve N280 (with Externally Regulated Compressor)

NOTE:
- Connecting service station. Pressures, Checking on Vehicles
- Observe test conditions. Refrigerant Circuit, Checking Pressures (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 and Coolant Fan V7 are vehicle-specific.
- Pressures must be measured at service connections; component locations of these connections are vehicle-specific Heating, air conditioning or Air conditioning.

Specifications

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

Low pressure:







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 in amps
C. Permissible tolerance range (applicable to compressor capacity utilization of 10...90%)

NOTE:
- Given high ambient temperature and a low engine speed, compressor may for example no longer be able to adjust pressure on low-pressure side to value given in graph. Compressor is actuated with maximum specified control current, however delivery volume is no longer sufficient at this engine speed to reduce pressure on low-pressure side to value in graph , air conditioner "Guided Fault Finding" function and Heating, air conditioning or Air conditioning.
- 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 of A/C Control Head E87 or Climatronic Control Module J255.
- High pressure measured by High Pressure Sensor G65 or A/C Pressure/temperature Sensor G395 is displayed in measured value block of A/C Control Head E87 or control head, Climatronic Control Module J255.
- Low pressure settles as a function of control current for A/C Compressor Regulator Valve N280 and control characteristic of expansion valve within compressor output range in tolerance band.
- Under unfavorable conditions (very high ambient temperatures, high humidity), compressor output may not always be sufficient to attain the specified value.
- If compressor capacity utilization is greater than 90 %, pressure on low-pressure side may be in excess of tolerance range "C" shown in graph (compressor output no longer suffices).
- Specified operating current for A/C Compressor Regulator Valve N280 must be greater than 0.3 A to ensure reliable valve actuation.
- In "maximum cooling output" setting, control current for A/C Compressor Regulator Valve N280 is regulated to approx. 0.65 A (up to 0.85 A). This measured value is vehicle-specific and displayed in measured value block.
- At absolute pressure, 0 bar corresponds to an absolute vacuum. Normal ambient pressure corresponds to 1 bar absolute. On the scales of most pressure gauges, 0 bar corresponds to an absolute pressure of 1 bar (can be seen from -1 bar mark below 0), air conditioner "Guided Fault Finding" function and Heating, air conditioning or Air conditioning.













NOTE:
- It is not initially necessary to flush the refrigerant circuit with compressed air and nitrogen when this problem occurs. 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 in the receiver (adjust quantity of refrigerant oil). Refrigerant circuit is then to be evacuated for at least 3 hours.
- With this fault, evaporator may ice up although quantity of refrigerant in circuit is OK.
- Problem with Evaporator Vent Temperature Sensor G263 can also cause icing-up of refrigerant circuit. If this problem is encountered, also pay attention to measured value of Evaporator Vent Temperature Sensor G263 , air conditioner "Guided Fault Finding" function and Heating, air conditioning or Air conditioning.