Help with 1HP Capacitor Start Motor

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  #1  
Old 07-24-15, 05:05 PM
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Help with 1HP Capacitor Start Motor

This motor came to me broken. It's a Sears table saw motor, 3450 RPM.

When I first got it, it wouldn't spin, just strain. The shaft turned freely by hand, even when straining. I thought it would be the capacitor, and I had a replacement left over, but the new cap didn't help.

I took it apart, found the centrifugal switch to be very sticky, cleaned out the whole thing, then lubed the switch. Voila, it works. Brag to my wife, my kids. A few days later it stops again. It'll run under power with no load, ie belt off, but it just strains with the belt on, even pretty loose.

All these symptoms STILL sound like a bad cap, but it's not that. I've checked all the internal wiring, and it's all solid and in the right places. One of the bearings is pretty rough, but it spins easily. I'd replace it in normal circumstances, but I'm unemployed and I'd rather limp along on this motor a while longer.

Any ideas folks? Many thanks in advance.
 
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  #2  
Old 07-24-15, 07:42 PM
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Welcome to the forums.

A motor model number would be a great start.
That could be a run capacitor. What's the size and voltage on it ?

A 250v cap would be a start cap..... a 370/440v cap would be a run cap.
 
  #3  
Old 07-25-15, 04:47 PM
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Hey PJ,

The motor is a Craftsman 113.12171 from the mid-'80s. The start cap is 216-259mfd 120v. I don't see a run cap anywhere and I've had it apart. I didn't mention in my earlier post that the windings look good, no burn marks or obvious damage.
 
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