Refrigerant Circuit Switches, Sensors, and Related Connections

Refrigerant Circuit Switches, Sensors, And Related Connections

NOTE: Refer to vehicle-specific refrigerant circuit for switching pressures, switch removal/installation and switch layout/design Heating, Ventilation and Air Conditioning.







A/C Refrigerant High Pressure Switch F23

Function:
Switches coolant fan up to next speed setting in the event of pressure increase (approx. 16 bar) in refrigerant circuit.







A/C Refrigerant High Pressure Switch F118

Function:
Switches off compressor in the event of excess pressure in the refrigerant circuit (approx. 32 bar).







A/C Refrigerant Low Pressure Switch F73

Function:
Switches off compressor in the event of pressure drop in the refrigerant circuit (approx. 2 bar).

Connections with Valve for Refrigerant Circuit Switches
- There are different threads for switches on high and low pressure sides.







- Only valves and O-rings resistant to R134a refrigerant and the related refrigerant oils are to be used.
A - Connection (soldered in)
B - O-ring
C - Valve (with O-ring)

A/C Pressure Switch F129







This pressure switch has 3 functions:
1. Switches coolant fan up to next speed setting in the event of pressure increase (approx. 16 bar) in refrigerant circuit.
2. Switches off air conditioner in the event of excessive pressure (approx. 32 bar) caused for example by inadequate engine cooling.
3. Switches off air conditioner in the event of insufficient pressure (approx. 2 bar) caused for example by loss of refrigerant.

NOTE: The A/C Pressure Switch F129 replaces the A/C Refrigerant High Pressure Switch F23, the A/C Refrigerant Low Pressure Switch F73 and the A/C Refrigerant High Pressure Switch F118.

High Pressure Sensor G65







The High Pressure Sensor G65 is installed instead of the A/C Pressure Switch F129 or the A/C Pressure/temperature Sensor G395.

The A/C Pressure/temperature Sensor G395 ( "grey" housing at present) and the High Pressure Sensor G65 ( "black" housing at present) currently only differ in terms of housing color and attention is therefore to be paid to correct assignment on replacement. As these two sensors emit different signals, the relevant control module can only evaluate the signal to which it has been matched.

The High Pressure Sensor G65 generates a square-wave signal or data telegram when voltage is applied. This signal changes with the pressure in the system.

The downstream control modules (coolant fan control module, Engine Control Module (ECM), A/C Control Head E87, Climatronic Control Module J255 etc.) use this signal to calculate the pressure in the refrigerant circuit and to actuate the coolant fans, fan motor and A/C Clutch N25 accordingly or to modify actuation of the A/C Compressor Regulator Valve N280.

A/C Pressure/Temperature Sensor G395







The A/C Pressure/temperature Sensor G395 is installed instead of the High Pressure Sensor G65.

Externally, the A/C Pressure/temperature Sensor G395 ( "grey" housing at present) and the High Pressure Sensor G65 ( "black" housing at present) currently only differ in terms of housing color and attention is therefore to be paid to correct assignment on replacement. As these two sensors emit different signals, the relevant control module can only evaluate the signal to which it has been matched.

When voltage is applied, the A/C Pressure/temperature Sensor G395 exchanges information via the air conditioner data bus system "LIN bus" ) with the corresponding control module. The relevant control module uses this information to calculate the pressure and temperature in the refrigerant circuit and any faults detected are signalled to the control module.

The temperature measured by the A/C Pressure/temperature Sensor G395 differs on account of the design of the A/C Pressure/temperature Sensor G395 and the component location from the actual temperature of the refrigerant in the refrigerant circuit. It is therefore not evaluated at present by all control modules and used for air conditioner control.

This information is used for example by the control head, Climatronic Control Module J255 to calculate the pressure in the refrigerant circuit and to actuate the downstream control modules (coolant fan control module, Engine Control Module (ECM) etc.) by way of the data bus system. These control modules then regulate, for example, the coolant fans and engine accordingly.

A/C Compressor Regulator Valve N280







The regulator valve is installed in the compressor. It is actuated by the A/C Control Head E87 or the Climatronic Control Module J255. The pressure on the low pressure side is influenced by way of the regulator valve, thus regulating the temperature in the evaporator.

NOTE: The A/C Compressor Regulator Valve N280 is part of the compressor and cannot be replaced separately.







A/C Compressor Speed Sensor G111

Inductive sensor
The sensor pulses (4 per compressor revolution) and the engine speed enable the A/C Control Head E87 or the Climatronic Control Module J255 to calculate belt slip.

If the belt slip exceeds a specified value, the compressor is switched off by the control module via the A/C clutch.

NOTE: The sensor is installed in Audi vehicles with compressor drive via poly V-belt and Zexel compressor.







Refrigerant Temperature Sensor G454
The Refrigerant Temperature Sensor (with temperature-dependent resistor) is installed e.g. in high pressure line in vicinity of the compressor.

In the refrigerant circuit, there is a direct relationship between temperature and pressure, if there should be too little refrigerant in the refrigerant circuit, the temperature in the refrigerant circuit rises higher than intended for this pressure while A/C system is running.

NOTE:
- Installed e.g. in the Audi Q7 with specific engines.
- The A/C control head, Climatronic Control Module J255 evaluates pressure and temperature in the refrigerant circuit and switches off the compressor in the event the temperature increases above the value stored for this pressure.

Coolant Fan Control Control Module J293

(Not on refrigerant circuit)







This control module switches the A/C clutch and thus the compressor on and off. It switches the coolant fans and calculates the pressure in the refrigerant circuit on vehicles with High Pressure Sensor G65.