what type of compressor do you have? I have an ancient westinghouse 3yc industrial unit, and the switch you describe sounds similar. The big spring in the center of my switch is acted upon by a diaphragm that is plumbed into the tank. Tightening that spring will raise the pressure required to break the electrical contacts in the switch, giving you more psi. Be careful though, I played with mine before I knew anything about it, and it took a couple hours to straighten out. My unit was set up to come on at 200 psi and cut off at 250, so it took some tweaking to get it to run lower. I have it set to come on at 90 and cut out at 175. I guess my best piece of advice is to make small adjustments, and make a record of how many turns you move everything from stock. That way you can always get back to where you started if things get confusing.