My Sears motor just hums and then blows fuse?

by jim
(herrin il.)

This is a sears vertical 33 gal reciprocating compressor. The motor and pump turn free by hand. No bad bushing or bearings.


Three things come to mind immediately, Jim.

One, make sure you are not using an extension cord, or if you must, it is an industrial, large gauge cord. Two, your unloader valve is not working. To test, unplug the compressor, open tank drain to void tank, close drain, plug in and start. Does it? If so, your unloader valve may have failed, and the motor cannot overcome the additional load. Check out UNLOADER VALVE from the site map for details.

Three, your start capacitor may have failed. See the page on this site about testing capacitors for guidance on how to check them. There’s also a page about buying a new one if you need help there too.



A Sears 106.173781 air compressor

Sears 30 gallon 2 hp compressor – Blowing breaker

by Jeff

I’ve got a sears 30 gallon 2 hp compressor, approx 2 years old. When it comes on it blows the breaker about 50% of the time. Even when it only has a few pounds in it. I changed 20 amp breaks with no change. It is a 15 amp GE commercial motor. model #5KCR49TN2450AX Ser #UYFP29. Whats my solution??


Jeff, good question! 🙂

For sure you’ve got either a too great amp draw or a fault to ground.

That it doesn’t happen every time is interesting.

Do you have any other electrical appliance in the circuit that might cycle on when the compressor is starting? If there isn’t enough current to go around, that might be an issue.

You say, “When it comes on it blows the breaker about 50% of the time.” Does this mean that it starts and runs for a while then pops the breaker, or does it mean that it pops the breaker while it’s trying to start?

If the latter, I think it could be a failing pressure switch.

Post bit more info to this thread, and we’ll continue trying to figure it out with you.

Sears 921.153102 3 gallon 1 hp – overload reset switch?

does this unit have overload reset switch


If there isn’t one visible around the on / off or panel, then there may be one on the motor, but I do not know for sure.

I have examined the manual for the model 153100 ( I don’t have the manual for your model ) and it does not specifically refer to a motor reset or motor thermal reset, so I would need to see the motor to see if there was one.

Sears Compressors ~ breaker trips after about 2 seconds

by Tim
(Ashburn, VA)

Compressor is a Sears 25 gal 5 HP portable (electric). Had been working fine, but after using for about an hour the other day, the compressor kicked in automatically to fill the tank, and blew the breaker.

Compresssor runs slowly for a few seconds, then trips the breaker. With no pressure in the tank, it runs a second or two longer but still trips the breaker. I have tried several different outlets with the same result, including a dedicatd 25 amp circuit, so it’s not that. I have also tried turning the pump by hand it it rotates freely. Compressor is about 10 years old.

Check your unloader valve. I think that it has failed, and as a result, the motor can’t overcome the additional load on start up.

Not sure what that is? Go to the sitemap page, and look up Unloader Valve for more info.



Questions or comment about Sears air compressors that pop fuses or breakers? Maybe we can help. Please post with pictures of your compressors so we can see what you are asking about.