Switches and Sensors on Refrigerant Circuit and Corresponding Connections
Switches And Sensors On Refrigerant Circuit And Corresponding Connections
NOTE: For switching pressures, removing and installing switches and switch arrangement and version, see vehicle-specific refrigerant circuit.
A/C Refrigerant High Pressure Switch F23
Function:
Switches coolant fan to next higher stage upon pressure increase in refrigerant circuit (approx. 16 bar).
A/C Refrigerant High Pressure Switch F118
Function:
Switches off A/C compressor when there is excessive pressure in the refrigerant circuit (approx. 32 bar).
A/C Refrigerant Low Pressure Switch F73
Function:
Switches off A/C compressor when there is excessive pressure in the refrigerant circuit (approx. 2 bar).
Connections with valve for switches on refrigerant circuit
CAUTION:
- There is a danger of ice-up.
- Refrigerant will leak out if refrigerant circuit is not discharged.
- Refrigerant must be extracted before removing valve - C -. If refrigerant circuit is not opened within 10 minutes of extraction, pressure may form in refrigerant circuit due to evaporation. Extract refrigerant once more.
- Different threads for switch on high pressure and low pressure sides.
- Only valves and O-ring seals that are resistant to refrigerant R134a and refrigerant oil must be installed.
A - Connection (soldered in)
B - O-ring seal
C - Valve (with O-ring seal)
A/C Pressure Switch F129
This pressure switch has 3 functions:
1. Switches coolant fan to next higher stage upon pressure increase in refrigerant circuit (approx. 16 bar).
2. Switches off A/C system if pressure is excessive (approx. 32 bar), e.g. because of insufficient engine cooling.
3. Switches off A/C system if pressure is insufficient (approx. 2 bar), e.g. loss of refrigerant.
NOTE: A/C Pressure Switch F129 replaces the A/C Refrigerant High Pressure Switch F23, A/C Refrigerant Low Pressure Switch F73 and the A/C Refrigerant High Pressure Switch F118
High Pressure Sensor G65
This High Pressure Sensor G65 is installed instead of the A/C Pressure Switch F129.
When a voltage is applied, the high pressure sensor generates a square wave signal or a data telegram. This signal changes along with pressure in the system.
The downstream control modules (Coolant Fan Control (FC) Control Module, Engine Control Module (ECM), A/C Control Head E87 or Climatronic Control Module J255, etc.) use this signal to calculate pressure in the refrigerant circuit and accordingly to activate coolant fans and motor, A/C Clutch N25 or to change activation of A/C Compressor Regulator Valve N280.
A/C Pressure/temperature Sensor G395
CAUTION:
- There is a danger of ice-up.
- Refrigerant will leak out if refrigerant circuit is not discharged.
- The refrigerant must be extracted before the A/C Pressure/temperature Sensor G395 is removed. If refrigerant circuit is not opened within 10 minutes of extraction, pressure may form in refrigerant circuit due to evaporation. Extract refrigerant once more.
This A/C Pressure/temperature Sensor G395 is installed instead of the High Pressure Sensor G65 or A/C Pressure Switch F129.
The pressure signal is always being checked, where the temperature signal is only checked at temperatures above 0 degree C.
The Climatronic Control Module J255 operates with this information and accordingly controls the coolant fans and activation of the A/C Compressor Regulator Valve N280
A/C Refrigerant Shut-Off Valve N43
The flow of refrigerant in the second evaporator is switched on or off by the shut-off valve. It opens - switched by the programmer - when voltage is applied.
A/C Compressor Regulator Valve N280
The regulator valve is implemented into the compressor. It is activated by the A/C Display Control Head E87 or Climatronic Control Module J255. Pressure on the low pressure side is influenced via the regulator valve and thus regulates the temperature in the evaporator.
NOTE: A/C Compressor Regulator Valve N280 is a structural component of the A/C compressor and cannot be replaced separately.