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| This would be my first guess too - something gone wrong with the start switch. Perhaps the centrifugal switch is getting sticky and won't open up all the way under load. but with no load, the extra few RPM's are just enough to open it and not cause the rough running.
An AC motor does not have an armature - it has a rotor spinning inside of a stator. Bad bearings could also cause problems by allowing the rotor to rub against the stator as there is typically only about .015" air gap between a rotor and stator. Don't know if this would cause sparks or would cause the motor to ground out though. Either way, if you take the motor in for repair, have them replace the bearings anyhow since that would be an opportune time. | |
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Electric motors, how to diagnose?
