Saturday, December 17, 2011

How to Re-wire a Potted Motor, Part 7: Disconnecting the Motor Leads

Okay folks, time for us to get our hands on the machine.

Before removing the motor from your 201-2 or 15-91, we must first disconnect the motor leads. From here on in we’re going to need lots of different screwdriver bits, so be sure to read the entries on proper screwdriver bits if you’re unclear on this area; if you use the wrong type of driver and strip a screw in the middle of a motor re-wire, you’ll find it a huge hassle.

Step one is unplug the machine. Not at the wall, but at the terminal body.

Step two is to remove the single screw holding the terminal body on. (A Brownells bit #270-5 fits perfectly.) You’ll find this screw has often been overtightened, so remember to press hard into the screw as you unscrew it, to reduce the chances of strippage. After you’ve removed the screw, keep it safe, we’ll need it again in a sec.

Gently pull the terminal body towards you and downwards. Now at this point you’re going to see one of two things:

Best-Case Scenario:

If you see this, you're lucky.

I call this the Best Case Scenario because even though we can see some exposed wire that needs to be replaced, everything is still clean and there is no oil damage. Which leads me to the next example….

Worst-Case Scenario:

If you see this, you're unlucky. But don't despair, we'll get to it.

This is a different machine than in the previous photo, and as you can see, we’ve got big problems. Never mind the exposed wiring and cracked, rotted insulation--there is massive oil damage. Someone has over-oiled this machine, causing the wiring insulation to get oily and melt and run into the terminal body. Look at how the light switch on the left is covered in thick, black, hardened goop.

Although this problem is fixable, this is a LOT more work than the Best-Case Scenario, and will require a separate series of entries. If your machine’s terminal body looks like this one, let me know in the comments and I’ll begin preparing that Worst-Case Scenario series of entries. In the meanwhile I’ll continue on here for the Best-Case Scenario machines.

Unwire the terminal body

Remove the three thumbscrews from the terminal body. There are only two motor leads, but we remove all three thumbscrews because the wires are often covering one another.

Next, gently pull the ring connectors off of the brass studs. You may want to mark the wires with tape, according to what color they connect with (red, black or yellow.) And be vigilant--there may or may not be a brass washer on top of the ring connectors, and if you pull them up too fast, the washer may go flying off into space. It’s happened to me and I never saw that washer again.

Gently pull the rings off of the brass studs...

...but keep your eyes open for these washers!

Next, isolate the two motor leads--the two wires leading up to the motor--and pull them gently to the side. They may be plastered against the side of the machine, but don’t be shy about pulling them off; if the machine needs re-wiring, then these wires have to go, no matter what.

Rewire the terminal body

After isolating the motor leads, re-connect the other, non-motor wiring. Then screw the thumbscrews back in place.

Put it back together, minus the motor leads

Next, screw the terminal body back into the machine. Not tightly, just enough to keep it in place.
We do this partly for safekeeping--there’s no chance you’re going to lose the thumbscrews, brass washers, etc. if they’re attached to the machine--and partly to keep it out of the way: The next step will expose some potentially messy grease, and we don’t want that getting onto the inside of the terminal body.
Nice and tidy, in preparation for the next step

Go on to Part 8: Removing the Motor Housing


  1. I think I have a worst worst case scenario. Bare wires, snipped from the motor to the terminal body. But not to worry, I can tell which one is the white wire in the motor itself and now iwth your photo can tell that the white wire goes to #3 in the terminal. Whew. Thanks for that, Rain.

  2. No prob, Elizabeth. (And even if you couldn't tell which is the white wire, once we get inside the motor, there's a way to tell, which we'll get to soon.)

  3. For some reason my posts aren't getting through on these, but I will once more say good job Rain, and I would like to see the worst case scenario, too.
    Diana in CNY

  4. I have two 15-91's that need rewiring. At least one is a worst-case scenario, at best, so please, when you have a chance, can we see how you go about fixing your worst-case machine? I've never rewired anything, so these posts are invaluable to me and I'm sure a whole host of others. Thank you!
    Pat, on a cold foggy hillside just east of the Coast Range

  5. Great series, I wish I had seen something like this years ago. Patiently waiting for the next installment, thank you so much.

  6. Hi Rain, I have recently done a couple of worst case machines. Your notes were most valuable! In addition to the motor, the light had horrible wires, too. Replacing the light was the easier thing, so that's what I did; however, I would like to have a tutorial on that light fixture rewire if you do one.
    BTW, my motor rewire is complete, and the machine sews nicely. I do wish it had the pep of some of my other machines, though. There is no hesitation; I was just expecting more get-up-and-go.

    1. Hi K9, if you have more than one Singer button controller (foot pedal), try swapping it to see if it makes any difference. I've found that sometimes an improperly-tuned controller gives you the illusion that the motor is weak. In future I'll have to do a post on adjusting the controller to peak efficiency.

      - Rain

    2. Hi rain, could you do a post on light fixture rewire,as well as changing the light wire that run inside the machine.

  7. Hi Rain,
    I just came across a worst case scenario machine. The motor line's insulation even melted and adhered to the machine exterior all the way down to the receptacle. Is there a way to remove this with minimal machine-finish damage?

    1. Hi Jae, I've encountered this on two or three 201s, and each time I've been able to remove the melted insulation from the pillar with zero damage. What you want to buy is a product called Goop, or a similar product called Gojo. You should be able to find it at an auto parts store, and I've even found it sold at Chinese delis here in NYC. Read the package carefully to be sure there's no pumice in it. Also buy a big package of cotton balls because you can literally go through several hundred during this process.

      First remove the motor and wiring. Then, using the cotton balls, apply some Goop to the melted wiring insulation on the pillar and rub gently. (You don't want to rub too hard because the melted insulation itself can act as an abrasive and damage the finish.) You'll observe the cotton ball quickly turns black at the point of contact. Flip the cotton ball over or switch to a new one and repeat the process. You always want to be wiping with clean cotton.

      It will take a surprisingly long time and you will go through an ungodly amount of cotton balls, but with persistence you will get all of the insulation off. Be sure not to rub too hard, particularly when you get towards the end, as you don't want to rub the clearcoat off.

      Let us all know how it goes, or drop me a line if you have more questions.

      good luck with it,

      - Rain

    2. Thank you very much for this info, Rain. I hope my touch is as gentle as yours. Cotton balls, here I come ;)

  8. I'm doing my mom's machine, a 201-2 bought new for her when dad finally got a steady job in the late '30's. I've used it all of my life but when I pulled it out to make some jammie bottoms for winter, it had gooey slime pooled on the base. After wiping it clean I took it to my local wizard who took a look and said "$300 and then I can't say I can fix it".
    I haunted the internet for an hour before I found your magnificient tutorial on rewiring the Rube Goldberg that are my machine's works. Who would've guessed the wheel was the entrance to the motor! What looked to be the logical way was the path to disaster.
    Thank you so much! I've got it down as far as uscrewing the wiring... Today will be spent covering the dining room in plastic, myself in tyvec and tackling the grease pit that will be my machine after seventy six years of use. If you don't hear from me again, alert my husband to look in the dining room, under the gears and assorted other detritus.

  9. My machine is the worse case scenario. Every thing works but wiring is a mess. I've rewired the power cord and have disconnected the motor wiring from the terminal body. I have been carefully cleaning all the black gook of with a cloth. The wiring is very brittle. Then I found your site.

  10. when plugged in my motor runs constantly full speed ahead!y. The power is going directly to the motor the foot pedal is being by passed. What's wrong?