Automotive AC Repairing and Replacing – Schrader Valves and Check Valves

The service ports on AC systems are provided as a connection point for the manifold set or the AC machine. There is typically a low side service port as well as a high side service port. These service ports have a valve inside the port that is spring loaded and acts like a one-way check valve. There are two styles available: a Schrader-style valve or a ball-style valve.


The low side R12 service port is a threaded port that has a Schrader valve to prevent refrigerant from passing through the port when a service hose is not connected. This port is a 1/4-inch threaded


The low side R134a service port is a 13-mm quick-connect coupling that has a Schrader or ball-type check valve to prevent the refrigerant from passing through the port. This is the location where the blue service hose is connected, which allows diagnosis and service procedures to be performed on the


The low side R1234yf service port is a 14-mm quick-connect coupling that has a Schrader- or ball-type check valve to prevent the refrigerant from passing through the port. This is the location where the blue service hose is connected to the system to allow diagnosis and service


The high side R12 service port is a threaded port that has a Schrader valve to prevent refrigerant from passing through the port when a service hose is not connected. This port is a 3/16-inch threaded


The high side R134a service port has a 16-mm quick-connect coupling with a Schrader- or ball-type check valve to prevent the refrigerant from passing through the port. This is the location where the red service hose is connected to the system to allow diagnosis and service


The high side R134a service port has a 16-mm quick-connect coupling with a Schrader- or ball-type check valve to prevent the refrigerant from passing through the port. This is the location where the red service hose is connected to the system to allow diagnosis and service


The high side R1234yf service port is a 17-mm quick-connect coupling that has a Schrader- or ball-type check valve to prevent the refrigerant from passing through the port. This is the location where the red service hose is connected to the system to allow diagnosis and service


Schrader valves for the service ports are available in several sizes depending on the make and model of the vehicle. These valves look similar to tire Schrader valves but have special O-rings that seal the refrigerant in the


The ball-style check valve is available for low side service ports and is replaced as an assembly. This unit has seals, springs, and a special check ball device that prevents refrigerant from passing through the

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