I recently inherited a disk sander with a 6.5 amp motor. My grandfather had a standard 15 amp light switch hooked up to turn the sander on and off. My father had to take the thing apart to get it here. After rewiring the light switch back in place, the motor now trips the breaker instantly.

I thought maybe the contacts in the switch went bad, so I tried a new switch and got the same problem. I then ordered a safety switch for things like a table saw thinking maybe I needed a more heavy-duty switch. Still the same problem.

If I remove the switch altogether and just wire the motor right to the plug, it runs with no issues. It's only when I try to insert that switch that I have a problem.

Tearing my hair out on this one.


Motor close up - hard to see anything

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  • Comments are not for extended discussion; this conversation has been moved to chat.
    – Michael Karas
    Commented May 21, 2020 at 9:10

1 Answer 1


Based on picture and follow-on comments-

If it only trips the breaker with the switch insert, and runs without the switch in the circuit, you must be wiring the switch incorrectly.

From your picture, the black should be one side and the white on the other side. You have the wires going side to side, the black wires should be arranged vertical on one side and the white vertical on the other side based on the color of the terminals on the switch.

The Q&A area for the switch states that the black goes on one side and the white goes on the other side, not on top of each other.

You will get continuity on one side with the switch on, and no continuity when the switch is off. You will get no continuity from side to side, with switch on or off.

Please note, even if it work now, you may have damage the switch contacts (internal) by shorting the switch. I would replace with a new safety switch or with a normal light switch, switching only the black(hot) wire.

  • Looking at the age of this and not seeing any ground wires, it's probably a 2 prong plug. Those are easy to plug in "backwards" meaning the white wire would be hot and the black neutral. It's safest to use a double pole switch on plug attached equipment, even for 120 volts. Commented May 21, 2020 at 13:27
  • The root cause of the issue is wiring the hot and neutral on the switch. The reason for asking to do only the hot is to validate the wires are not being crossed. OP from my understanding was connecting black and white wires on the same side of the switch, tripping the breaker when the switch was turned on. I do agreed that both should be switch, but not until correct wiring procedure is established. Commented May 21, 2020 at 13:44

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