Craftsman upright compressor is slow starting and blows breaker.

by Gary
(Bossier City, La.)

I have a 30 gallon Craftsman upright. 919.167311 built in 2002. If there is no pressure in the tank it will run to about 100 psi, then it shuts off. It sounds like it is loading harder than normal as the pressure increases. If I cut it off at around 20 psi and then turn it back on the motor binds and trips the breaker. I don't know all the part names but I removed the small tube from the tank to the pressure switch and it ran like a champ. Dumping air obviously. I have been reading the blogs and assume it is the pressure switch. But am wondering, is the pressure release valve is in the switch box. Are we talking about the valve that has the ring on it that I can pull to release pressure. I call it a pop-it valve. Is the unloader in or on the side of my switch box/pressure switch? Any idea what the problem may be and can I clean or replace anything inside the 'pressure switch' if that is the problem. That thing is close to a hundred bucks and I'm cheap!! Do you recommend one from somewhere besides Sears.

Thanks,
Gary

____________________
Bill says....

Gary, a bunch of questions, for sure.

The pressure switch turns the compressor on and off at preset pressure readings. If, when the compressor tries to start, there is power running from the pressure switch to the motor, then the start side of the pressure switch is working. If the power flow to the motor stops when the pressure in the tank reaches the normal cut out pressure level, then the stop side of the pressure switch is working.

Pressure switches, typically, have either a small lever that juts out one side of them to operate the unloader valve, or have an internal unloader valve operating mechanism. It sounds like yours is the former. That unloader valve should be triggered by the pressure switch when the tank pressure reaches the cut out pressure level and shuts the compressor off. The dumps the air over the piston, allowing an easier restart.

You say "it will run to about 100 psi, then it shuts off". Is this the normal cut out pressure, or is the compressor stopping sooner that it should? Look to the pressure switch being the possible cause, if it is stopping sooner.

When empty, your compressor starts OK, but won't start under load. The first check I would make is to ensure that the unloader valve is actually working.

Check these out and post a comment here if we want to discuss your compressor further.

Cheers,

Bill


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Aug 31, 2011
Craftsman upright compressor is slow starting >>
by: Anonymous

I also have one in my shop that FOR the longest time every so often the compressor would occassionally hum or if I let it go long enough it would throw a breaker. Turns out that the circuit it was on was also the same circuit as my upright freezer

Aug 31, 2011
Gary
by: Anonymous

Moral of the story: Shorter cord, longer air hose!
Thanks

Aug 31, 2011
More info.
by: Gary

Well I may have wasted your time. I was using the compressor on a far side exterior outlet from the fuse box and then on a 100 foot extension. It is military with a plug box on the end of it. (It was for running power from a generator to GP type tents.) It is 16 gauge wire. Have used it for years without a problem. Anyway I moved the compressor to the garage where the fuse box is and it runs fine. Guess I need to check the wiring in the extension cord plug box.

Is there anything I should still be aware of or look for? Guess I needed to eliminate the potential problems outside of the compressor before pointing fingers at the compressor.

To answer your question my compressor is 150 psi and cuts off normally at 140. I saw on one blog that a guy was instructed to change the pressure switch to no avail, then the check valve, to no avail again, then the capacitor in the motor, with the potential of the motor slowly going out. This problem seems like a real headache.

Let me know if there is anything I should check or watch for. Thanks again.

___________________

Many folks think that an extension cord will run any electrical device over any distance. If folks considered the extension cord as a fuel line, with a fixed capacity of fuel flow, and the device they were using consumed more fuel than could get through the size of line, they would better understand why a small extension cord under-"fuels" an electric motor. Not only does the motor not run right, but it will fail much sooner than if properly "fueled".

B.


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Craftsman 20 gallon upright air compressor wont start under load

My 20 gal upright air compressor (mod # 919-165230) is kicking breakers and not starting when there is even a small amount of air pressure in the tank.

I replaced the capacitor thinking it might be an easy fix. Still having the same issue. Based on reading some past comments, it appears that replacing the check valve might be the next step.

On the diagram, it refers to this part as the "choke valve"....not sure if that is something totally different, but seems to match up on part # searches. Any help on where to go next would be much appreciated.

____________________
Bill says...

Before you dive in, can you tell me, is the unloader valve working? Maybe you could post a comment here to let me know.

Thanks,

Bill

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Oct 05, 2015
it lives!
by: Robert

thank's again bill. the new start capacitor fixed it. now even with 100psi in the tank when i hit the switch it cranks up amazingly quick. literally no hesitation. instant full speed. i'm impressed (and relieved).

the sears site recommended the unloader valve in their troubleshooting. i figured you'd tell me the same, but you did not...and you were right. i hope that makes you feel good because it sure made me feel good to see the thing working again.

-robert

Oct 02, 2015
Unloader check
by: Bill

That's a good as any way I know, Robert. Usually I do the "blow through" as a check for the tank check valve.

If the unloader goes "pssst" when the compressor cuts out on high pressure, and then after a second or two there is no air leaking from the unloader, and no air blows out of it while the compressor is running, then it's good.

I appreciate that you visited my site. Cheers.

Oct 02, 2015
thanks bill
by: Robert

the big black mallory start capacitor is dead as a doorknob. i ordered another and will post my result when it arrives.

curiously, while i had it apart i took out the unloader valve out and blew through it. i could not suck any air back in. is that a fairly safe way to assume it's good? just curious for the future.

thanks Bill i appreciate you!

Oct 01, 2015
Compressor won't start under load
by: Bill

It were mine, I'd be checking the start and run capacitors. See the page on this site about how to do that and what they are if you don't know.

Oct 01, 2015
i'm having the same issue. "wont start under load"
by: robert

mine is also a 919.165230, but strangely mine is a 5.5hp 25 gallon upright model. i double checked the model number twice.

my compressor also wont start under load. it initially starts and fills fine, but when it kicks back on it struggles for a few seconds and flips the breaker. this happens with as low as 15psi in the tank.

previously i blamed the wiring in my shop. however i just purchased a 110 mig welder. last week i had an electrician install (2)20A breakers, 6" below the breakers he installed 2 dedicated 20A outlets. the outlets and the welder work flawlessly, which leads me here. no extension cords.

if you'd like to see the setup, you may copy this to your browser: http://oi59.tinypic.com/16tbbr.jpg

can you point me in the right direction? i'm pretty handy at fixing everything fr everyone around me, figured i'd give this a shot.

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