air compressor stopped working, trips breaker

I was using an air chisel for about 30 minutes and then it tripped the circuit breaker at the service panel. When i reset the breaker it trips immediately. I tried another outlet/ breaker and it tripped also. My compressor is a craftsman 6hp 30 gal 120v 15amp single cylinder oiless. 8.6 cfm @ 40psi 6.4 cfm @ 90psi. I only use it on a 20 amp circuit and i use a 20 amp extension cord. I took the cover off the motor and i cannot find any obvious problems, everything looks brand new. I've had this compressor at least ten years with no problems. What is causing this to trip the breaker when i plug it in?

 

Try it on a different circuit, or give that circuit some time to cool down. If it works fine, I would conclude that the wire is hot, or the breaker is weak. I've heard that once some of the newer breakers trip once or twice, they need to be replaced.

 

I was using the compressor at my neighbors house. It does the same thing at my house a day later.

 

Take the belt off and spin the compressor and motor separately. Do they move freely? You should not be using an extension cord on a compressor. Add hose, not cord. What gauge is the extension cord?

 

no belt. piston and motor both move freely. 12 gauge wire in extension cord. trips breaker without ext cord. i try to put the plug into the oulet and i get a spark and it trips the breaker

 

Dead short in the motor winding maybe?

 

Dwashpa, I have the same compressor, about the same amount of time,with the same problem. After I bought a new compressor, and had some time to take the old one apart, I found out the starter capasitor was bad.

 

where's the capacitor? Inside motor housing (black cylinder), or mounted on top of housing (ilver cylinder)?

 

Nevermind, one is the start and the other is the run capacitor.