Quincy hydraulic unloader assembly replacement, part number: 110827-001.
This hydraulic unloader is used on Quincy compressors.
This valve senses when your oil pressure reaches above 14 PSI. When this happens it cuts off the flow of air that is going to the unloaders which allows the pump to build pressure.
When the compressor reaches max pressure and shuts off, the oil pressure drops below 14 PSI.
This allows air to pass through to the unloader on the compressor relieving the air off the head for a load free start up.