Auto A/C Terms - Glossary
High Side Service Valve - High Side Charge Port

Also called a charge port or access port, the high side service valve will be located on the system somewhere between the compressor and the expansion valve. That means it’s anywhere from the discharge port of the compressor, on the hose between the compressor and condenser, or on the liquid line of the system between the condenser and expansion valve.

Older R-12 A/C system service ports were threaded male flare fittings that the service hoses threaded onto. Typically, the high side port was smaller than the low side port so that they were not confused.

On R-134a systems, the service ports are known as quick coupler ports. They require couplers that will snap onto the charge ports in order to access refrigerant pressures.

Understand that even though older R-12 manifold pressure gauge sets may include hoses with threaded ends for R-12 systems, they can be converted to work with R-134a by simply adding the proper adapters.