Sunday, March 29, 2015

Rewiring Vintage Singer Sewing Machine For Polarity

Vintage Singer sewing machine old style AC plugs were not polarized; consequently the hot side of the circuit can run through either side of the machine.  The light socket can provide a shock even with the light switch off depending on how the non-polarized AC plug is inserted into the AC receptacle.

New AC plugs are polarized so it provides an opportunity to wire the machine in a safer manner.

I am providing a wiring diagram that depicts a polarized wiring path using a polarized AC plug.

It might be helpful to also note that polarity does not matter with regard to the controller and the motor.

I hope you find it useful.

Don't attempt the techniques explained in this article if you don't have electrical experience or are not certified in electronics.  Doing so may result in electrical shock and/or death.  If you decide to act on these techniques, you are doing so at your own risk.  It is recommended to have your work checked by a licensed electrician or certified electronics expert.


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  2. Odd that you indicate how to make it safe but then still show the controller on the hot leg. This could be even safer by swapping the singer bake light and controller ... That way the neutral runs through controller

    1. I'd rather have the neutral running through the motor and the hot running to the "switch" in the controller. It is normal wiring practice to run the hot leg to the switch... in this case, the switch being the controller.

  3. We just found a working Lady Kenmore using a model 6813 foot pedal with a damaged power cord. The plug attaching to the machine has three evenly placed slots, but it is a molded plug, so I would have to replace it or splice a new cord in front of it. Do you know if a replacement 3slot plug is available and how do I identify which lead into the connector to connect to the hot?