Troubleshooting air compressor

[vandersmash]

I was given a 10-year-old air Craftsman Air Compressor last year that wasn't working properly. So far, I've replaced both capacitors and the pressure switch and resealed all the leaky air fittings. It will run and build pressure, but not the proper pressure. It's supposed to cut off at 150psi, but it will only make it as high as 110-120psi. That's not all, though. It also won't restart at all. If I unplug it and come back to it later and plug it in, it will run again, but it will only make it up to about 80psi and still won't restart when it discharges. I've tried to look up more info on the compressor, but the model number is conveniently scratched off (see picture). Any ideas about what I should try next?

 

[larry4406]

Welcome!

My guess is that the unloader is not working and/or you may have an issue with the check valve between the compressor outlet and the tank.

 

[vandersmash]

I'll give that a shot. Thanks.

 

[The Cobbler]

It's supposed to cut off at 150psi, but it will only make it as high as 110-120psi. That's not all, though. It also won't restart at all. If I unplug it and come back to it later and plug it in, it will run again, but it will only make it up to about 80psi and still won't restart when it discharges.

first thing is compare your pressure to a known accurate gauge .. that set point is (usually) adjustable in the pressure switch . don't rely on an unknown pressure gauge
not restarting, does it try to start or just does nothing?

 

[finn]

The check valve was leaking on my little 30 year old PC pancake compressor. It healed before I got around to buying a new one or I burned out the windings because of the high current draw when starting.

This thread reminds me that I should order a new check valve.

 

[vandersmash]

first thing is compare your pressure to a known accurate gauge .. that set point is (usually) adjustable in the pressure switch . don't rely on an unknown pressure gauge
not restarting, does it try to start or just does nothing?

It just does nothing.

 

[The Cobbler]

sounds like either a bad pressure switch or a bad connection .

 

[finn]

It just does nothing.

Take the cover off the pressure switch. The switch on my well pump fell apart once. It was pretty obvious when I looked at it with the cover off.

 

[Shoreline_]

You replaced the pressure switch did you adjust the pressure to the desired cutoff setting? Turn that ***** in so it never turns off. Run it. When you get to 140 psi back off the adjustment until the compressor stops. Turn forward a smidge. Done.

 

[Buckaroo5]

Also having trouble with a 20+ year old Craftsman 6HP 30 gal 150 psi compressor with AO Smith motor. It will start at low pressure and build pressure appropriately but will not restart when it drops below the lower pressure set point (around 110 psi). It tries to start maybe 3 times (a few revolutions) and then trips the breaker. I have checked both capacitors and they are good. I am hearing a hiss when it shuts off so I think the unloader is working. I suppose the next step is the check valve, right? Is there a way to confirm it is bad or do I just replace it and see what happens?

Sears Parts Direct says check valve no longer available, part AC-0631. Maybe this is the part I need (A19712) but Craftsman not called out. Under Black & Decker, very close to my model number (mine 919-167310 vs 919-16732 Type listed)?

https://www.jackssmallengines.com/jacks-parts-lookup/part/devilbiss/a19712?gad_source=1&gad_campaignid=16705372762&gbraid=0aaaaad_uacipmqmeykqad0nlcws3phojq&gclid=cjwkcajwuuprbhaneiwa2ji8etbyrye86gb5mxk9skrkqnhve8uewfetstvy4azhbt2yx8v4rv_cfxocox8qavd_bwe

 

[Buckaroo5]

Jack's confirmed A1972 was correct part but not in stock with no replenishment date from DeWalt. Ordered one from Ebay although likely a knock-off.

 

[Beerhippie]

Also having trouble with a 20+ year old Craftsman 6HP 30 gal 150 psi compressor with AO Smith motor. It will start at low pressure and build pressure appropriately but will not restart when it drops below the lower pressure set point (around 110 psi). It tries to start maybe 3 times (a few revolutions) and then trips the breaker. I have checked both capacitors and they are good. I am hearing a hiss when it shuts off so I think the unloader is working. I suppose the next step is the check valve, right? Is there a way to confirm it is bad or do I just replace it and see what happens?

Sears Parts Direct says check valve no longer available, part AC-0631. Maybe this is the part I need (A19712) but Craftsman not called out. Under Black & Decker, very close to my model number (mine 919-167310 vs 919-16732 Type listed)?

https://www.jackssmallengines.com/jacks-parts-lookup/part/devilbiss/a19712?gad_source=1&gad_campaignid=16705372762&gbraid=0aaaaad_uacipmqmeykqad0nlcws3phojq&gclid=cjwkcajwuuprbhaneiwa2ji8etbyrye86gb5mxk9skrkqnhve8uewfetstvy4azhbt2yx8v4rv_cfxocox8qavd_bwe

Unloader valve. Classic symptoms.