by Mike

Want to make repairs to an older Sears Air compressor but pressure switch is no longer available?

I am trying to clean up and make repairs to an older Sears Air Compressor (model # 919.174320). The handle is broken, the electrical cord frayed, etc.

I have purchased parts from but the pressure switch is no longer available. I suspect that this switch has been replaced in the past as it has a square D switch which I doubt came on a Sears Compressor.

The switch has two sets of contact points of which one set is broken off and has been glued on. The glue failed and I would like to replace the switch.

I can’t find a p/n on the Square D switch. This switch has an on/off lever and what I suspect is an “unloader” feature. By this, I mean that the switch has a separate small aluminum tube attached from the compressor cylinder head. The actual switch sits atop a nipple from the storage tank but the smaller tube comes from the compressor head.

I can purchase from Grainger if I just can figure out what part number I need. Your help would be appreciated.

You are quite correct that most DIY type compressor pressure switches incorporate the unloader valve as part of their design and the line from compressor head is attached to the unloader valve in the pressure switch.

I have uploaded a picture to show how the pressure switch toggles a small valve (1 in image)  at the end of the “tube from the compressor head” on my home compressor, thus allowing air trapped over the piston to escape when the pressure switch toggles to off and that process depresses the pin on the valve.

I can’t be sure what model or part number of pressure switch will suit your compressor best.

I am fairly sure that any “standard” compressor pressure switch will work, though I appreciate it’s hard to buy one on-line, though mostly you can easily send it back if it doesn’t work.

You might read this page about buying a new pressure switch as it gives you all the details you’ll need to find a new one.

A Sears compressor wont shut off even after PRV releases.

by Gary K
(Disney OK)

Sears 100 PSI compressor wont shut off even after PRV releases.

I replaced the pressure switch and it still does the same thing. Today I found the valve spring in regulator was rusted to zilch.
Could this be the problem? If so, where can I find one?
Gary, when the compressor was working properly, what was the cut in pressure and what was the cut out pressure settings? What pressure is the PRV releasing at?

The pressure switch is what controls the on/off of the compressor, switching it on when the pressure drops below cut in, and turning the air compressor off when the pressure reaches cut out.

If the compressor never reaches the cut out pressure level, it will run and run to overheat and self destruction is a possibility.

If the air compressor tank pressure exceeds the cut out setting of the pressure switch, then the pressure switch has failed.

If the PRV is letting go before the tank pressure reaches cut out, then it’s the PRV that is suspect.

Regardless, the regulator spring has no control over the start/stop of your compressor, though you will be hard pressed to set your downstream pressure with that regulator, if the spring is pooched.

If the new pressure switch is emulating the old, and you have installed the new one correctly, then let me know the pressure specs as I noted above as a comment here.