Craftsman 5hp 20 gallon (model#919.165200) trips breaker

This compressor keeps tripping my garage breaker at start-up! It will start up a second or two then trip the breaker. It ran fine the other day! but I don't think it ever cut back On when it hit the Cut-in pressure (110)Cut-Out pressure is set at 130?


I remember I was getting low air pressure but I was finished anyways. Now it won't run without tripping the breaker in a second or two! Regulator seems fine, Pressure switch seems OK, Unloader valve works In/Out before it trips out, Check Valve OK, Safety Valve OK, the motor isn't binding any the fan turns fine, what do I check next? and where can I get parts? I Need some Help Please!

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Bill says...

Good on you for checking all the things you have. This is the kind of post that helps me help you.

Two more things to check. What's changed in the circuit? Do you have any other electric equipment pulling current from the same line as the one that feeds the compressor? Make sure not.

From what you are saying, and if there is no additional draw on the power supply, you may have a capacitor problem. It holds a boost of power that used when the motor starts up, as starting electric motors draws much more power than they need when they are running.

If the capacitor is weak or failing, the boost isn't there for the motor, it tries to start, pulls too many amps for the circuit, and your breaker trips out after a couple of seconds.

It were me, I'd take my motor and capacitor (usually on the side of the motor) to a motor rebuild shop and have both checked out.

Cheers,

Bill

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Craftsman Air compressor immediately trips fuse

by Matt Ruffer
(North New Jersey)

3HP GE Motor trips fuse as soon as I flip the switch. I have removed the motor from the tank and all switches. I disconnected both capacitors and connected a cord directly to hot and ground on the block. (saw video's on youtube to bypass the start and run capacitors). Fuse still blows instantly. Bad windings??

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Bill says...

In my vast (-:) experience with motors, I would say that you have a fault to ground. Could be windings, could be a wire loose, pretty hard to tell from here.

Maybe you could post again the youtube link for the bypass of the start run capacitors? Folks (me too) would be interested.

Cheers,

Bill

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craftsman 33 gal 6 hp blowing fuse

by keni thomas
(nashville, tn)

hi Bill I have read all the posts and based on what you've said there, I think the problem is the unloader valve. before I go and buy new parts i wanted to check with you and be certain thats the next step.


when the tank is empty the motor fills it up and it shuts off as it should
as I use the air and the pressure in the tank goes down, the motor tries to come back on as it should. Thats when it blows the breaker.

I have to bleed all the air out of the tank and only then will it start up again.

seems from what you have been saying in the threads that this points to the unloader valve.

if this is correct, is that the part I go to sears and order? "Hi I need an unloader valve for my craftsman compressor"

thanks for you help Bill..

God Bless

Keni

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Bill says....

Hi Keni. Good on you for reading and figuring out what is likely your air compressor problem.

Double check and make sure it's the UNLOADER VALVE. You will know from reading that page that the unloader is likely operated by your pressure switch.

Dump the air again, close the drain, fire up the compressor, and watch the unloader as the air in the tank gets close to the normal cut out level.

As the compressor stops, you should see the unloader valve operate, and if you are close enough over the very loud compressor, hear the air dump out of the unloader.

If the unloader valve isn't operated by the lever from the pressure switch (unless you have an internal unloader, in which case it means a new switch) then maybe it's the switch and not the unloader.

So check, before you buy.

And yes, if it is the unloader valve itself that is the problem... it may only be crud inside bunging it up, and if you disassemble it, you may bet it working again.

Cheers,

Bill

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