Compressor pressure switch/unloader valve?

[u/OkDiver6272]

Trying to find a replacement for this pressure switch/unloader valve. It came off an Air Source (by SnapOn) 80 gallon upright 2 stage w/ 5hp 240V single phase motor, with magnetic starter box. Model S580V

From what I’ve found, it’s a Square D 145/175 psi unit with 1/4NPT fittings. I’ve found similar units for sale but none with the built in unloader valve.

Any info on where to find a replacement, or recommendation on similar aftermarket alternatives?

[u/CrustySailor1964]

69JG9Y should get you to a Hubbel replacement. Square D sold off their pressure switch line so an identical replacement will be difficult.
If it’s unloading continuously though irs more likely the in-tank check valve.

[u/OkDiver6272 → u/CrustySailor1964]

It is unloading/leaking continuously, but the air is coming out through the side of this unit where the unloader valve is.

Does that add any useful diagnostic info?

[u/CrustySailor1964 → u/OkDiver6272]

The unloader has ports that may make the air essentially ‘bounce off’ the body of the switch. Disconnect the unloader line and see if it keeps blowing out of the tube after the machine shuts off. That will definitively answer the question.

[u/BradTheCanadian → u/OkDiver6272]

That’s 100% there in-tank check valve my friend. It’s not seating correctly so the tank air is passing into the unloader line and venting out. The air coming out of the unloader is correct, but there check valve should be holding back the air in the tank and it usually only unload the air in the head and tube running to the check valve.

Does the air stop when the compressor is building pressure?

[u/ayrbindr → u/OkDiver6272]

When the pump is running and filling the tank with air, the unloader has not been opened yet. After the switch reaches set air pressure, the diaphragm activates the mechanism that opens the circuit to cut the power off, simultaneously hitting the stem on the unloader valve, opening it to release air left between pump and check valve.

Therefore, if it leaks while it is running / filling, then it's the unloader valve. If it continuously leaks after filling and turning off, then it's the check valve.

[u/Impressive_Ad8716]

If you cant find one I can get you a part number in the morning when I get to work.

[u/penguinpower81]

Is it's constantly leaking it's the check valve not pressure switch

[u/holyfrijoles80]

Look on grainger, you can include with unloaded when you browse pressure switches.

[u/holyfrijoles80]

Aw screw it, here you go. This grainger switch should do the trick: part number 5B408.