Quote:
Originally Posted by
My air compressor quit working. The motor just hums and will not start.
The belt and comporessor unit are free. I can easily spin it by hand,
which means it's not the motor bearings either. The motor is a 120V AC
about 1/2 HP. It has a capacitor on top, so I'm thinking that is a
starting cap. How likely is it that the cap is bad? I guess the only
other problem would be bad windings, but that often causes smoke. I
dont have smoke.
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Does the electric motor output shaft turn.
If it doesn't, and the motor just hums, then my guess would be a bad starting capacitor. You don't have to buy a new capacitor from the company that made the motor or the compressor; any motor rewinding shop will have them for sale.
In a capacitor start motor, it's the capacitor that causes the magnetic field of the start winding to be offset by 90 degrees from the magnetic field of the run winding. It's that difference in timing of the magnetic fields that provides the torque to get the motor to turn. Without a working start capacitor, what the motor's rotor is seeing is an OSCILLATING magnetic field which doesn't provide the torque necessary to get the motor turning.
I'd definitely replace the start capacitor.