Singer 15-90 Restoration: Part 5

This will be my next to last post in my Singer restoration series, because I’m almost finished! Last night I repaired all the electrical components, with a lot of help from my husband Matt. If you haven’t yet read the other posts here is part 1, part 2, part 3 and part 4.

My machine’s wiring was in terrible shape. When I first plugged in the machine the foot pedal wasn’t controlling the motor, the motor was running off and on, but the light worked. The first thing I did was dismantle the electrical system, the 15-90 is unique because the electrical system is removable, here is the diagram of the electrical components on the 15-90:

Once off the machine I inspected the wiring. Basically the motor and light had crumbling insulation, which meant exposed wires, and the foot pedal’s ring connector wasn’t attached anymore. You can see all the damage best on this picture of the 3 pin terminal:

Supplies for repair:

To re-cover the exposed wires we used heat shrink, which is plastic tubing you can cut to size and shrinks tight when heat is applied. Technically you are suppose to use a heat gun, but a lighter works just fine. We started with the motor, here it is before:

One side was completely exposed, the other had crumbly old insulation still intact. I stripped away the old insulation down to about an inch from the motor.

Matt then covered the wires in electrical tape, then heat shrink tubing and applied heat.

Here is the completed repair to the motor:

We followed the same procedure for the light’s wiring:



The foot pedal repair was a bit more complicated, here is the wiring before:

I stripped the old insulation down an inch or so and Matt clamped on a new ring connector. We tried at first to re-use the old ring connector, but the wires were soldered/melted into it. So in the middle of the project Matt ran to Wal-Mart to buy clamp on ring connectors. If you need to use new ring connectors use the 3 pin terminal to determine the correct size. You could also solder the old wiring back together.


At the other end of the foot pedal the connections were solid, but there was a little wire poking out, which I covered with a small piece of heat shrink.


To finish I re-connected all the ring connectors on to the 3 pin terminal, here is a technical drawing of the correct order from the 15-91 adjustments manual:

Pin 1(yellow): foot pedal and light fixture. Pin 2(black): foot pedal and motor. Pin 3(red): motor and light fixture

We plugged the power cord in and everything worked, light came on no problem and the foot pedal once again controlled the motor! I put the whole electrical system back on my machine, and it looked great. I need to order a new drive belt before I can test its sewing abilities but I don’t foresee any problems.


This machine has come a long way from the thrift store trash it was before. In my next post I will be purchasing a new drive belt and doing some sewing with my completely restored machine.

Having problems with your own vintage Singer? I’m no expert but I would love to help you puzzle out your problem just leave me a comment.

UPDATE: How to Clean & Restore Vintage Singer Sewing Machines the eBook is now available in the Zounds Shop! Save and print all of the information you need to fix your machine! 

More to Read!


  1. William says:

    I just picked up a 1949 Singer 15-90 in working order and with attached table (basically same as in your photos). I have some of the same deterioration to the wires although the machine still runs. It looks like someone did a bit of a hack job to it a while back as I don’t have the plug for the wires. The lead is stripped and hard wired to the motor. I’d like to restore it back to factory. Thanks for the blog posts. It’s nice to see people out there with similar interests and situations. Keep up the good work!

  2. Sara says:

    You are just awesome. Thank you so much for posting all the steps and including photos and advice. I just bought one of these and I will be needing this information in the days to come. I just want to express my gratitude for your excellent blog.

  3. Carolyn says:

    I sat down to make curtains and my machine was running strange. Since I recently replaced parts I began checking the belt etc. When I touched the light cord the machine began running on it’s own and was producing a smell. That’s when I noticed the exposed wires. I almost cried. I received this machine from a neighbor 25 years ago and the thought of replacing it was heart breaking.
    I used your posts to replace other odds and ends. I couldn’t believe there was a solution to this issue as well. Thank you so much for taking the time to show how to fix this electrical problem! I hope to have this machine for years to come and hand it down to my girls.

  4. Jennifer says:

    I have just purchased this very you know if I could disconnect the motor and change it back to a crank?also where did you get your new belt? Thanks so much you are amazing.

  5. Brian Keith Ceglarek says:

    I restored a 15-90 for my mother about a year ago, the wiring on hers looked in much the same disarray as yours did, insulation just crumbling off, in my experience when insulation starts to degrade in one spot it is highly likely to be degraded throughout. Upon dismantling the motor and stripping the power cord i found multiple spots in which the insulation was just dust and the wires were frayed and the outer jacket showed no signs of damage! A cheap and very easy solution is to buy 2-3 indoor extension cords clip the ends you don’t need and attach crimp terminals. They are made of bare copper rather than the no longer used “tin” copper singer used and the improvements we’ve made in insulation materials means you won’t have to worry about internal shorts for many more years of use.

  6. DJ says:

    I have a Wizard sewing machine with motor which worked perfectly until it fell off a truck during a move. Have been using your Singer restoration info to restore, your machine is almost identical. It was coming along well, but when I put the wheel and belt back on, suddenly it would not operate the needle. The machine motor runs and turns the wheel, but not the machine. I have taken it off and put it back on repeatedly and cannot discover why, obviously something is wrong. I suspect it has something to do with the bobbin winder but cannot figure out what it could be. Any suggestions. Thanks DJ

  7. I just wanted to tell you how much I appreciate you posting this tutorial to your blog. I recently rewired an upgraded motor for my Singer 15-90 and your blog took all the guess work out of the process. Thanks again!

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