Air compressor check valve, 1/2" Compression x 1/2" MPT with 1/8" hole; plug hole if not needed.  https://mastertoolrepair.com/1-8-blk-steel-plug-s-h-100b6e/ If the small unloader (bleeder) valve on or under your pressure switch leaks constantly...

Old Part Numbers: 034-0184The Condor 12AC2FAKH OEM pressure switch replacement is an MDR12 style, 4-port, 1/4" female NPT pressure switch with manual on/off switch and 90-degree push-connect style unloader valve and is preset to 125/155 PSI. Replace the...