Mechanic Glossary

A/C Low-Pressure Valve

A service port valve on the suction line of the A/C system used by technicians to add refrigerant or measure system low-side pressure.

The A/C low-pressure valve (suction port) is a service connection point on the thick aluminum line running between the evaporator and the compressor. It contains a spring-loaded Schrader valve core that opens when a service coupler is attached. Technicians use this port to evac the system, check low-side pressure, or recharge the refrigerant.

This valve can slowly leak refrigerant if the internal seal dry-rots. The plastic cap is designed to act as a secondary seal. It is critical to keep the cap screwed on to prevent dirt from entering and jamming the valve open.

Frequently Asked Questions

It is located on the thicker aluminum line of the A/C system and has a physically smaller quick-connect port diameter than the high-pressure port.

Yes, by using a specialized valve core tool that unscreves the core. If you use a standard tool, the pressurized gas will blow out, so you must use a pressurized core remover or evacuate the system first.

This is normal. The low-pressure line carries cold, low-pressure gas back to the compressor, causing moisture in the warm engine bay air to condense on the cold pipe.

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