Question about Craftsman 3 gal. Air Compressor, 1.5 hp, Horizontal k

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Motor running at half power

I have a Craftsman Air Compressor, #921.153101, that all of a sudden acts like it's being given half volatage. The motor runs, but the contacts are rapidly opening and closing, and the motor is running at about 1/2 speed. I put power directly to the wires going to the motor, bipassing the regulator value, same result, so I know the pressure valve is not causing it. I'm guessing it might need Part #E100247, Running Capacitor, but I don't know. Is there some kind of test I can perform before getting the new part and hoping I guessed right? thanks, John

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  • Anonymous May 16, 2009

    my 3 gal 1 hp aircompressor will not turn off it just keeps running wat can be the problem


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It sounds more like the centrifugal switch in the motor (if it has one). In that case it's not running at half voltage -- it's only running with half its windings.

The switch would be on the shaft on the output end of the motor just inside the case. It could be sticking or it could have burned contacts, or it could be broken (it has springs in it).

The switch spreads as the RPM increases making and breaking contacts.

The run capacitor is probably okay, since a bad one would only keep it from running not starting.

Posted on May 08, 2009

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