The Schrader valve uses the same type af valve core as used on automobile tires. It has a spring-loaded, gasketed core which closes when released and opens when depressed.
Often used on systems not equipped with service shut-off valves. In such cases, the Schrader access ports may be used any time because they are selfsealing. The valve cap should be in place during normal system operation.
When evacuating or recovering refrigerant or recharging a system with Schrader valves, a valve core remover/replacer tool is often used. This tool removes the valve core and holds it back out of the way inside the tool to eliminate restriction and provide full refrigerant flow or faster evacuation. Use of the tool roughly doubles the speed of the charging, recovery, or evacuation procedure.
When the core remover is used, it is screwed to the Schrader valve. The manifold hose is connected to the remover rather than to the valve. Without the core remover, the manifold hoses must have built-in Schrader valve core depressors or an accessory core depressor must be fastened between each valve and the manifold hose.