A/C Low Pressure Port
The service connection port on the low-pressure (suction) side of the A/C system used for charging refrigerant.
The A/C low pressure port is a quick-connect service valve located on the larger, cooler aluminum pipe of the A/C system (the suction line running between the evaporator and the compressor). It is the primary port used to add refrigerant to the system.
The low-pressure side of the A/C system typically operates between 25 and 45 PSI when the system is running. To prevent service errors, the low-pressure port is physically smaller than the high-pressure port, ensuring that recharging equipment cannot be accidentally connected to the high-pressure side.
A technician connects a manifold gauge set or a recharge bottle to the low pressure port to monitor suction pressure and add refrigerant. The port contains a Schrader valve that can leak over time, requiring a plastic dust cap to keep dirt out and provide a secondary seal.