Air Compressor Question

[Peter Stahl]

Does anyone know how the pressure switch on a air compressor works. Mine doesn't seem to be functioning. I got the compressor second hand from my BIL. I had to put in a new valve plate and it pumped up fine but wouldn't shut down and the relief valve blew open. It did sit for about 8 months before I put the new part on. Looking at the switch, I'm guessing it runs until it sees a certain tank pressure. Any help would be much appreciated.

More info, the switch is a Furnas Electric Co., Cat# 69WB108425 set to come on at 90 psi - off at 125 psi.

[Jim DeLaney]

Could be your BIL futzed about with the pressure switch settings. That black and silver pair of screws on the front of the switch are supposed to control when the compressor cuts in and out, Try backing off the silver screw to see if it'll lower the cutoff pressure so the relief valve doesn't pop. Once you achieve that, then you can 'fine tune' it to the proper 125 psi setting by trial and error. Ditto for the low setting. Back it off until the compressor begins recycling at something less than 90 psi, then 'sneak up on' the proper setting.

Might take a while to get it set right.

If none of this works, then a new switch is in order. Grainger or McMaster Carr should have what you need in their catalogs.

[Steve Jenkins]

also make sure the contacts aren't frozen shut. You should be able to open them by hand or with a screwdriver to pry a bit. disconnect the power first

[Peter Stahl]

Could be your BIL futzed about with the pressure switch settings. That black and silver pair of screws on the front of the switch are supposed to control when the compressor cuts in and out, Try backing off the silver screw to see if it'll lower the cutoff pressure so the relief valve doesn't pop. Once you achieve that, then you can 'fine tune' it to the proper 125 psi setting by trial and error. Ditto for the low setting. Back it off until the compressor begins recycling at something less than 90 psi, then 'sneak up on' the proper setting.

Might take a while to get it set right.

If none of this works, then a new switch is in order. Grainger or McMaster Carr should have what you need in their catalogs.

Looks like you were right Jim. Didn't want to mess with them but made a couple adjustments and I think i have it pretty close. Thanks for you help.

[Peter Stahl]

also make sure the contacts aren't frozen shut. You should be able to open them by hand or with a screwdriver to pry a bit. disconnect the power first

Thanks for the reply Steve. Contacts were ok, looks like the pressure adjustment screws were out of adjustment.