Switches and Sensors on Refrigerant Circuit and Connections

Switches And Sensors On Refrigerant Circuit And 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







Function:
Switches coolant fan to next higher stage upon pressure increase in refrigerant circuit (approximately 16 bar).

A/C Refrigerant High Pressure Switch







Function:
Switches off A/C compressor when there is excessive pressure in the refrigerant circuit (approximately 32 bar).

A/C Refrigerant Low Pressure Switch







Function:
Switches off A/C compressor when there is excessive pressure in the refrigerant circuit (approximately 2 bar).

Refrigerant Circuit Connections with Valve for Switches

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







This pressure switch has 3 functions:
1. Switches coolant fan to next higher stage upon pressure increase in refrigerant circuit (approximately 16 bar).
2. Switches off A/C system if pressure is excessive (approximately 32 bar), e.g. because of insufficient engine cooling.
3. Switches off A/C system if pressure is insufficient (approximately 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







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

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 Compressor Regulator Valve







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.