Valves and Switches

NOTE:
- Check shift pressures, switch and sensor removing and installing, as well as switch locations in refrigerant circuit.
- There are several different versions of switch and sensor.
Refer to "A/C System, Servicing". Service and Repair

Pressure relief valve







The pressure relief valve is mounted on the compressor. At approx. 38 bar (551 psi), the valve opens to vent excessive pressure. When system pressure is reduced to approx. 30-35 bar (435-508 psi), the valve closes to prevent total refrigerant loss. The refrigerant will not run out completely.

A/C refrigerant low pressure switch -F73-

Function







Switches A/C clutch -N25- OFF if system suction pressure is too low (low refrigerant charge). This switch protects the compressor if the refrigerant system is empty.

A/C refrigerant high pressure switches -F23- and -F118-







Both switches are incorporated into a single housing.

Function of -F23-
Switches coolant fan -V7- to second speed when A/C system pressure increases.

Function of -F118-
Switches A/C clutch -N25- OFF if system pressure is too high.


NOTE: The illustration shows switch from Audi A4.


Valve connections for pressure switches







Schrader valves installed under A/C system pressure switches allow switch replacement without discharging refrigerant system.
- A/C system low and high pressure switches use different size threads.
- Use only the correct switches and O-rings specified for use with R-134a refrigerant and PAG oil, refer to "A/C System, Servicing". Service and Repair
A - Switch connection (soldered)
B - O-ring
C - Schrader valve insert


NOTE: Always refer to the latest parts information to ensure correct switch application.


Connections for quick coupling adapter on refrigerant circuit


NOTES:
- Use only the specified quick coupling connectors resistant to R-134a and respective refrigerant oils.
- Different connections for the high and low pressure sides (outside diameter)
- Before removing the valve or valve inserts, discharge refrigerant system. Service and Repair
- Always reinstall cap over service valve (with sealant).


High pressure service connection with Schrader valve







A - Service valve connection (soldered)
B - Schrader valve insert
C - O-ring
D - Cap with seal


NOTES:
- Only a high pressure service valve is used for A/C system servicing. A low pressure service valve is not installed in the A/C system. Perform all A/C system service operations (i.e. discharging, evacuating, and charging) through the high pressure service valve only.
- Before removing the valve insert from the high pressure service valve, discharge refrigerant system. Service and Repair