# bench grinder problem



## chrisb (Jan 3, 2008)

I have a Ryobi 8 inch bench grinder tha is about 6 years old. When I turn it on the motor hums but cant get the wheels rotating.
It stated doing this a while back so I would give the wheels a spin and the motor would get it up to speed, but not anymore.
The wheels turn freely so there is nothing jammed. I don't know much about ac motors. Aren't these multi stage motors?
Is this capacitor problem?


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## Michael Glavin (Jan 2, 2009)

Chris 

More likely than not it’s a STARTING circuit issue… Single phase electric motors typically have a mechanical centrifugal switch which engages the start winding on power up, once the motor comes up to RPM the start winding drops out via the start switch. Some motors have an electronic switch which does the same thing, without the mechanical consideration. 

Yes the capacitor could be the problem, or the aforementioned “switch”. The switch is simply a set of contacts or points that mechanically open when the appropriate rpm is reached. Sometimes the points are stuck or dirty and pitted from arcing, the mechanical linkage fails to open or the start capacitor simply fails. 

Your description suggests the start circuit is not viable, as you’re able to spin it up and it takes off. If you’re in need of parts or assistance a local motor repair/rewinding company is the place to go… 

Michael


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