Briggs and Stratton 074004 10 gallon air compressor just hums

Briggs and Stratton 074004 10 gallon air compressor just hums when I turn it on and trips the breaker on the power strip I have it plugged into. Have tried plugging it directly into the wall and it still just hums so I turn it off within 3 seconds.

Is the motor shot? Some relay? This is an electric compressor.

I'm in the middle of a suspension job and this thing just quit on me in the middle of it. I haven't drained it in a while, so I went to drain it and since I can't build pressure hardly anything is coming out. I also haven't changed the oil in a while, but I'd say its "medium" dirty and is definitely at the half fill mark where it should be.

Hope somebody can help. Van is stuck in the garage and the compressor really helps move things along.

 

Can you turn it by hand?

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Often times it's the capacitor that's failed. It gives the motor a kick in the butt to get going.
Capacitor [201801GS] - $26.40 at eReplacementParts.com

 

First do as Cheese suggested and see if you can turn the compressor by hand, with it unplugged of course. If you can turn it then I would check the capacitor. Is it puffed or are the ends bulging out? If so it's shot. If it looks OK you can test it with a volt/ohm meter that can test capacitors. If you don't have that any volt meter set to ohms can be used. Make sure the cap is discharged by letting it set for an hour or short across the two contacts with a old screwdriver. Then put the leads of your meter on the cap's contacts. The needle should swing to the right or digitally show current flowing. Then the needle should drop to zero as the capacitor becomes charged.

 

Turn what by hand? Remove a cover and inspect to turn what?
So, I'm checking for the motor being seized up here? If it moves, its probably still ok?

I have a digital multimeter..... so if I set it to ohms (after I let the cap discharge) all I'm looking for after an hour of it sitting is 0.00 resistance right?

I think its the cap too, because I haven't run this compressor without always having the right amount of oil in it. I guess I should've drained the air tank more often though... Wouldn't that contribute to it going dead faster? The thing is only 5 years old and might get used 20 times a year. Pretty low use if you ask me.

 

You have the shield over the belt that drives the compressor from the electric motor? Take off the shield and try to turn the compressor over with the belt by hand. If you can't, take off the belt and see if the motor is froze up or the compressor.

 

And, no you are not simply looking for it to read zero ohms. You should see high resistance when you initially connect to the cap but over time size it will decrease. How quickly it drops depends on the size of the capacitor. Generally it's a matter of a few seconds. Once it has reached capacity it should read almost zero. Then if you reverse the leads it will do it again. This will only tell you that it can act like a capacitor and that it is not shorted or open. You need a capacitor tester to determine if it still has it's stated capacity.

 

Correct about reading the ohms, however, it will be the other way around and the ohms will start low, and gradually work toward infinity as the capacitor charges.

 

I tested the capacitor for continuity only with it completely disconnected and it started only in the 2.0+ range and settles at 1.9 ohms steady..... again this is without current on it. Does that tell us anything?

 

If it never changed from that, I'd say the capacitor is shorted.

 

Thanks cheese. I'll report back when I replace it.

 

New Capacitor fixed it. Started up immediately... no delay like it used to. I played around with getting a cheaper capacitor of more "beefy" build... but I could never really figure out if getting one that had a higher wattage/voltage tolerance would work, so I bought an OEM Briggs and Stratton brand OEM capacitor.