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Faunsdale, AL | Sounds as if your motor has a problem, not your starter or pressure switch. If it were a 3phase motor, then yes, that symptom would sound more like a starter problem, but single phase motor is going to either run if the starter makes good contact or not run if it doesn't. It won't be sitting stalled and humming like a 3phase motor will.
I would have the motor checked or if you can do it, check the running amps as it gets up to the shutoff pressure. If it's overloading, you may have a bad run capacitor, a bad bearing etc. Remove belts and run to listen to motor bearings, also spin the compressor by hand to check it for noise and binding not related to the compression stroke. I doubt there is something wrong with the compressor if it makes good pressure and doesn't knock or squeek while running etc.
If the motor hums and fails to start and that is when it trips off, check the centrifugal starting switch and starting capacitor. It sounds as if the capacitor(s) may be weak or the starting switch is not cutting the starting winding in like it's supposed to. When you are running the motor without belts, listen as it slows down. You should hear the centrifugal switch click and then a soft scrubbing sound as the motor begins to coast down after you turn off the switch. If you don't hear that, the motor isn't ready to start and will trip out the next time it is turned on. Even if the centrifugal mechanism is clicking and shifting properly, the switch contacts may be burned (temporary solution is to file them back smooth) and the switch needs replacing. Or could be just a weak capacitor or burned wire etc. They don't last forever, just almost! | |
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1960's air compressor
