# How to rewire old grinder



## jkk (Mar 28, 2010)

We found an old grinder at an auction. It has 3 wires from the motor and uses a capacitor. Unfortunately, some of the wiring is missing. How do I rewire this thing?


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## joecaption (Nov 30, 2011)

Make, model, a picture of the wiring and name plate would be a big help.


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## jkk (Mar 28, 2010)

It appears to be a Central Machinery TDS250, trying to get some pictures.


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## joecaption (Nov 30, 2011)

Look like this one.
http://www.made-in-china.com/showro...JCbeEInRx/China-TDS-Series-Bench-Grinder.html


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## jkk (Mar 28, 2010)

Pix of motor and capacitor with wire colors.


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## joecaption (Nov 30, 2011)

Someone's going to also need a picture of the name plate.
Why is the cap. off?
Need to know if it's 120/240.
I would have just brought it to a local electric motor shop and let them figure it out.


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## jkk (Mar 28, 2010)

It's 120VAC. It came like this, cap detached.


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## jkk (Mar 28, 2010)

OK, I've learned something. Single phase motors have 3 wires: Common, Run and Start. Largest resistance between any 2 wires means those 2 are Run and Start, other wire is Common. Least resistance between Common and 1 of the other 2 wires means that that other wire is the Run wire. By process of elimination, the remaining wire is the Start wire.
Capacitor is in series with the start wire and AC; AC also connects to the RUn wire. 

this assumes an internal cutoff/centripetal switch that cuts out the Start path after spinup.


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## Focused2 (Jan 2, 2013)

This diagram says what you just said: 









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Good luck, Joe


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