I have sanborn compressor in which the brand new pressure switch needle valve opens when compressor switch opens (off) allowing air to leak by.
Needle valve is located on side of switch connected to 1/4" line that runs to top of compressor cylinder head.

Any adjustment to internal mechanism that opens and closes needle valve. ?
It works in conjunction with contact points

I'm half tempted to snip the needle valve pin shorter
Hoping there is an adjustment instead

Sure enough
Removed check valve and guts were shot

Too bad I didn't troubleshoot before buying new pressure switch
Oh well , spare on the shelf

Thanks much for such quick response
Saved me ruining new pressure switch