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How To Rewire A Vintage Singer Sewing Machine Three Connection Terminal Block

Hello everyone today we are going to be showing you how to re-wire an old Singer sewing machine with the three wire terminal block.  Singer used this type of terminal block set up for a vast number of its machines, Variations were found on everything from the tiny 221 Featherweight to the 400 series family. Including the 66, 99,201,301,306,319, and of course the 15 series. We will explain the different ways the machines were wired using the basic design and how it evolved through the years.

rewire singer three connection terminal block

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I usually don’t like to get brand specific when we are talking about general maintenance and or cleaning up the machines to bring them back into smooth running order. But this time we need to delve into the known –unknown and explain a little about the specific wiring of the Singer terminal blocks. Notice the plural, yes they used the same blocks above the motor mount for a long time and for a variety of machines. The fun part is they used the same terminals on the block itself for the motor and the light but they changed and evolved the points of connection for the power and for the controller.  Because of this factor, it can look very confusing when the diagrams don’t reflect the visible change on the machine itself. So to help to eliminate the confusion I am going to try to explain why they look different but electrically function the same way.

We are going to begin at the terminal block on the back of the machine without the power plug plugged into it. The block is held in place by a single screw above the three brass pins of the terminal block. By removing the screw the terminal block is freed from the machine and can be turned over to gain access to the wires and the thumb nuts which secure the wires to each individual terminal. Old wires will harden and can make turning this over difficult to do. If the wires are that hardened with age and use, it is time to replace them anyway. From the back side we can see terminal designation numbers and in some cases, the numbers are still color coded as well. Terminal #1 was originally YELLOW in color and the necessary wires were YELLOW also. Terminal #2 was BLACK and all the wires connected were BLACK and terminal #3 was RED with only RED wires attached. All that was needed was to match the wire colors with the proper color terminal and the machine practically wired itself. Although it is possible to acquire replacement wire of the proper color it isn’t always feasible to do when most replacement parts are going to come shipped with black wire leads and replacement wire for the controller or the power cord will be from hardware stores typical inventory, commonly black, brown, or white. Colored tape or number tags/stickers can be used to designate wires if desired. Paint can fade or crack away but the number will always be there. And with that thought in mind, we will only be using the # designations and not the color as a guide. I will still use L1-L2 to keep our wires from getting crossed up.

We are going to begin by wiring our motor and our light to the terminal block. Starting with our L1 (switched wire) for the LIGHT we will connect it to terminal #1. Our L1 wire from the MOTOR will always go on terminal #2. Our L2 wire from the LIGHT and the MOTOR will always go together on terminal #3. This part of the wiring doesn’t ever change it will always be wired this way.

  When our MOTOR CONTROLLER is not wired to the power cord plug-in, and if it does not have a dedicated plug-in of its own then it must be wired to the back of the terminal block. To do this one of our wires from the CONTROLLER will become L1 and it will be connected to terminal #1 with the L1 from the LIGHT. The second wire from CONTROLLER will get connected to terminal #2 with the L1 wire from the motor. This is all of the wiring needed at the back of the terminal block. With this configuration, our power cord is simply a two wire plug-in with L1 going to the plug-in socket that matches terminal post #1 and L2 going to the plug–in the socket that matches terminal post #3. The downfall of this variation was simply the controller was permanently attached to the back of the terminal block and could not be removed for travel or storage.

The second variation of the wiring was to remove the controller wires from the terminals of the block and add them to the power plug. The L1 of the controller is still making the connection with L1 from the power plug. Only now it is on the plug-in side of the terminal block. The second wire from the controller is still making contact with the L1 for the motor because it is now wired to the #2 terminal connector on the power plug side of the connection. This configuration allows for the controller and the power plug to be removed for transport or storage.

The final variation of this basic wiring system also came with some physical changes. The terminal block no longer mounted to the motor mount. Instead, it was changed into a modular socket that was incorporated into the pillar of the machine. The terminals were still the same and the wiring diagram didn’t change. The terminal connections did however change. The connections are no longer thumbscrews instead they are soldered connections or they are soldered pigtail extensions and the actual connections are either wire nuts or push to lock connectors, Some of these machines have even deleted the center pin terminal from the modular socket. Even so, they still use the three wire terminal plug-in power cord and a dedicated terminal socket added to the body of the machine for the foot controller.  The socket would match a two wire plug-in attached to the controller. The wires from the mounted socket would, in turn, find their way back to the terminal block  #1 and #2 exactly like the first variation with the difference being now the controller has the capability of being unplugged from the machine for storage or transport. All of these variations use the same basic wiring schematics but they change the point of contact for the motor controller.

I hope some of you got a laugh from my struggles to explain the how’s and why’s of the Singer 3 terminal wiring system. I hope in some small fashion it helps cut through some of the confusion when looking at different  Vintage Singer sewing machines and trying to rewire them.

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Until next time enjoy your machines your way,

rewire vintage singer sewing machine three connection terminal block

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Would you like to comment?

  1. Great article. My brain, however, got lost by the time I got to the third variation. I would have like liked to see a diagram showing how the wires went. Love your topics.