Air Compressor Pressure Switch

Pressure switch is rated to pump to 125 psi, shut off, and restart pumping at 100 psi; and the safety valve is rated at 125 psi. How do you adjust the pressure switch to lower the pressure to 120 psi or so, so the pressure switch shuts off before the saftey valve pops open?

Thanks for your help and suggestions.

This is an 8 year old air compressor that I have had since it was new. The problem began with the unloader continually leaking after pump up and I did not know what was causing it at first. To investigate I messed with the pressure switch where the unloader is housed. I pulled the pressure switch apart and lost control of the process because of the powerful springs inside. I then read somewhere how the unloader works to unload pressue off the piston (after a shut down) so at the next start-up the unit does not have to start with pressure already on the piston. I realized that the check valve was bad and causing the unloader to vent the tank pressure. I replaced the check valve. And because of the damage I did to it, I replaced the pressure switch. The safety valve blew when it pumped up to ~125 psi (however, the gauges are the cheap ones that came with the compressor so I am not sure what the exact pressure is). I replaced the pressure switch with another new one from Sears and the same thing happened. I replaced the safety valve twice also with the same results. The unloader no longer continually leaks when I turn unit off with pressure still in the tank, so the original problem seems to be fixed.

The new pressure switch does not have a nut on the spring like suggested by someone responding to this site; it seems to have a very special adjusting device (requiring a special tool). At first I thought that it was a special torque bolt but that is not the case. It looks more like a fixed plastic dowel in the center with a donut-like ring of circles around the center dowel. I think that I need to find where I can get the special tool.

Any ideas?

Can you possibly use a Torx type wrench (L-Key) or driver? These type tools can be purchased at a hardware store or via a catalog such as McMaster-Carr.

Ralph

Good luck.

Sounds like something weird going on over there in your compressor. Anyway, to adjust the pressure switch, remove the cover and screw the nut one way or the other that sits on a washer on a spring over a threaded rod looking thing. I think you unscrew it a bit to lower the operating range.

First, did this just start happening spontaneously, or did you get this thing used and are trying to get it working? Certainly don't mean to offend, but make sure it's the safety valve releasing and not the unloader. If this problem is being caused by the unloader, you may have some faulty valves in the compressor head or be missing a check valve, depending on how your unit is supposed to be set up.

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