I bought a nice Craftsman vertical air compressor. Scared the you-know-what out of me when I first used it this past weekend. Supposed to shutoff at 180 p.s.i. Well, it kept running until the popoff valve did it's thing. How do I adjust the pressure regualtor (I am assuming it is mis-adjusted and needs some tweaking) to have it shut the compressor off at the desired pressure? Thanks in advance.