Reader Questions: Rewiring a 99?

All photos in this entry by Azul from California

Azul from California writes,

I was excited to discover your motor rewiring series, but I have a model 99, which does not have the potted motor and does involve a light switch. The motor is mounted on the side, as seen below.

What I have is a Singer 99-13 (according to the Sandman Singer identifying page) from 1937 which I picked up off the street. It’s in excellent cosmetic shape, but the wiring is in bad shape and down to bare metal in parts (mostly due to my boyfriend pulling away the corroded/melted bits).

I do know how to solder, and have access to the necessary tools and materials (although not yet, alas, the Chapman screwdrivers). My boyfriend knows how to repair electrical stuff in general, but does not have Singer-specific knowledge, although he’s enthusiastic and unworried about this (“it’s a light” and “it’s a motor,” he says). I did take the machine to a local repair place, where they seemed to think the wiring problem not too bad, they doubted that there was internal damage inside the motor, but of course would have to take it apart to know for certain.

My question is this: Do you think your tutorial, along with general principles of electrical repair, would be sufficient to work on this motor, although it’s not exactly the same type as the one in your tutorial? Or are there Singer specific issues that would make you recommend instead taking it to a professional, to for example avoid electrocution :o), or messing up the machine further? I’m not sure if you’re able to answer that, but thought I’d ask.

First off, congratulations on the free 99! That's an awesome find.

Secondly, good on your boyfriend for pulling off the rotted wiring insulation. I’ve seen sellers completely ignore that, as if hoping it will go away. As you can see, the wiring can easily come into contact with the body of the machine, which is all metal. That’s bad news if left untended.

To answer your question: While electricity is obviously dangerous if not handled properly, there is no Singer-specific issue I can think of that would prevent someone with knowledge of “general principles of electrical repair” from correctly re-wiring your motor.

Because we live in a country where people love to sue each other, I think I cannot just tell you to go ahead and do it. But the "sideboard-mounted" motor on your 99 (I put that in quotes because “sideboard-mounted” is not an official term, it’s just what I call it) is a simple and basic universal motor, the same you'd find on a 66, a 206, a 15-90, or a 201-3. The Featherweight 221 would also have a similar motor, with slightly less power. Bottom line: The principles of re-wiring yours would be the same as in the potted motor tutorial, and at the very least you would not have to deal with the worm removal shown in the potted motor tutorial (though you would still have to deal with brushes, grease wicks, the washer on the armature shaft, et cetera). Your motor simply turns the pulley sticking out of it, which in turn drives the belt, simplifying things a bit.

As long as you competently re-wire the machine in the exact same configuration in which it originally was, and using the proper materials, I would think you'd have no problem; but of course I do not have first-hand knowledge of you and your boyfriend's exact skill levels.

Also be aware that if worse comes to worst, you can buy simple replacement motors and install those on your machine, should you not feel like tackling the job. The reason I wrote the tutorial specifically for the potted motors is because those cannot be replaced with new motors due to their unusual design (i.e. the way that they fit onto the machine).

If you do decide to buy a new motor, I recommend Sew-Classic sewing machine supplies. While I've never bought a replacement motor from them (I always re-wire mine myself, to save money and because I find it satisfying), I've bought many other parts from Sew-Classic. Jenny, the woman who runs the company, is knowledgeable, responsive via e-mail in case you don't know exactly what you need, and has a (well-deserved) great reputation. She’s my go-to person when I need parts.

If you do decide to tackle it yourself, remember to take lots of photos as you disassemble the motor, so you have a reference for re-assembly. And a replacement motor is less than $25, which should take some of the pressure off.

Good luck with it,

- Rain

The Complete “How to Re-wire a Potted Motor”

If you are arriving at this entry for the first time, this is a comprehensive guide on how to re-wire the potted motors found on vintage Singer 15-91 and 201-2 sewing machines. It is my attempt to walk someone with zero experience through the entire process.

For your convenience, here are links to all 20 entries in the series. This way you can bookmark this page as a Table of Contents and quickly get to the entry you need.

Part A: Skills Building

1: Wire, Wire Stripping and Wire Braiding
Learn about the tools and wiring basics you’ll need to know to re-wire a motor.







2: Tools & Materials Required for Soldering
Learn what equipment you'll need to complete basic wire soldering.

3: Learning to Solder
Learn and practice basic wire soldering.

4: How to Terminate Your Wires
Learn how to create connections for attaching wiring to power terminals.

5: Covering Wire Joints with Heat Shrink Tubing
Learn how to clean up exposed wiring.

6: The Underwriter's Knot
Learn how to tie wiring into a strain-relieving knot.










Part B: Motor Disassembly

7: Disconnecting the Motor Leads
Learn to detach your sewing machine’s power terminal and wiring.

8: Motor Housing Removal
Learn to take the motor off of your machine.

9: Grease Wick Removal
Learn how to remove those grease wicks and where to get replacements.

10: Motor Brush Removal
Learn how to take those motor brushes out and look for signs of motor trouble.

11: Armature & Worm Removal
Learn to remove two crucial parts of your motor.

12: Detaching the Field Core
Learn how to safely crack the motor open.







 Part C: Making Repairs

13: Cutting and Prepping the Motor Leads
Learn where to cut the bad wiring off.

14: Replacing the Motor Housing Grommet
Learn how to remove a cracked rubber grommet, where to get a new one, and how to put it in.

15: Soldering On New Motor Leads
Learn where and how to solder on the new wiring.

17 (Yes, this is out of sequence): Cleaning the Commutator
Learn how to clean off a crucial element of your motor.







Part D: Motor Re-assembly

16: Re-attaching the Field Core
Here we start putting the motor back together.

18 (Yes, this is out of sequence): Re-installing the Armature and Worm
Learn the tricks behind putting these two crucial parts of your motor back together.

 

19: Re-installing the Brushes and Grease Wicks
Learn to easily re-install these correctly.

20: Hooking It All Back Up
Here in the final step we finish up the wiring, run the motor in, and put it all back together.








[A caveat: I hope you'll be able to bring your potted motor back to life with new, safe wiring, as shown here. But please be aware that these steps are not an absolute guarantee of success, as a small percentage of motors may be completely burned out, which is currently beyond my capabilities.]

How to Re-wire a Potted Motor, Part 20: Hooking It All Back Up

Now we’re at the final step to getting your machine back up and running!

Start by sliding your newly-renovated motor onto the shaft.

Tighten the two motor mounting screws securely.

Then, unscrew the terminal body. Note that I’ve tucked the two motor leads behind the terminal mounting bracket. This is so that we can determine the proper length to cut the tails.

Now we’re going to make new connections on the ends of the wires. As we went over in Part 4, you can either make your own eyelet and solder it, or use crimp-on connectors.

Option 1: Self-Made Eyelets

The self-made-eyelet-and-soldering route requires plenty of wire, which is why we’ve left the “tails” of the motor leads so long. You’ll need to calculate where to cut the wire such that you’ll have plenty of material to form your ring. I suggest measuring and practicing on a scrap piece of wire first, so you can be certain where to cut and strip in order to produce a ring that will still reach the post it needs to connect to in the terminal body. If in doubt, cut too long, not too short!

Option 2: Crimp-On Connectors

Here I’m going to do crimp-on connectors, which requires less length and is easier for me to execute. I generally determine where to cut by letting the terminal body hang naturally, supported by the lighting wires that are still connected, and then drawing the motor lead over the knob that it will fit under. I then pinch the wire to the side of the knob furthest from the motor, as shown in the photo, and cut there. This will make the final wire long enough that I can comfortably manipulate it into place.

Next I strip the wire ends to the length required for a crimp-on connector, just 1/4" or so.
 

Then I gather the connectors and, very important, I immediately cut two pieces of 1/8” heat shrink tubing about 1/2" long.

I slide the heat shrink tubing onto the wires first…

…and only then do I attach the connectors and crimp them on.

Then I slide the heat shrink tubing down into place, as seen below. You’ll notice that now I’ve pulled the motor leads OVER the terminal mounting bracket.

I’ve done that so that I can get the wiring a good distance away from everything else, to comfortably fit a lighter under the heat shrink tubing.

Now they’re heat-shrunk and ready to go.

Re-Attaching the Wiring
When the ring connectors are ready, tuck the wiring back UNDER the mounting bracket, in their final position. Pull the red and black wires over to their appropriate posts on the terminal. (Here I’m working on a 201-2, which has a light switch, and you’ll observe I’ve had to thread the black wire underneath a different wire that arches over it, connecting the light switch to the red post.) If you have a cabinet-mounted machine, connect the foot controller wires too, even if the machine isn’t in the cabinet yet. We need to do some testing.

After connecting the right wires to the right posts, we tighten up the thumb screws. Get all three of them as absolutely tight as you can with your fingers.

Now it looks like this. Be sure you’ve got the motor leads tucked BEHIND the bracket…

…then screw the terminal back into the machine. Do NOT overtighten this screw. The terminal body is made of plastic and easy to break. You only want to get it tight enough that it doesn’t wiggle around when you plug the cord into it.

I’ve grossly overexposed the next shot so you can see how the motor leads come down unobtrusively from the motor and disappear behind the mounting bracket.

Now we’re at the moment of truth!

Running the Motor

I plug the machine back in without re-attaching the handwheel, because I want to run the motor with no load--that is to say, not powering the rest of the machine--to ensure that it runs smoothly. This way if the motor doesn’t run, I know it can only be the motor that is the problem, and not some jam somewhere else in the machine.

Then I get the button controller up on the table. (And obviously, you should not stick your fingers inside the motor housing for any reason!)

Here are the results:



That’s the sound of a potted motor 201 running with no load. Sounds very different than when it’s connected to the rest of the machine, no? Sort of reminds me of a jet engine. I’ll continue running it for a few moments to ensure it runs consistently. And if you’ve inserted new brushes, you ought to run the motor for five minutes or so anyway, to wear the brushes in.

Warning #1: If you run the motor as I’ve done in the video above but it sounds different--for example, if it buzzes first and starts haltingly--STOP and unplug the motor immediately.

Warning #2: If you run the motor for a few minutes and it gets warm, that’s fine, particularly if you’ve been running it full tilt. But if it gets HOT, please STOP and unplug the motor immediately.

Both of those warnings are signs that something is wrong with your motor, either in the field core, the windings or the armature itself. And that something might be dangerous, which is why we ought to unplug the machine immediately. Sadly, those problems are currently beyond the scope of this blog.

But hopefully, everthing has turned out fine.

Re-attaching the Handwheel

It’s my habit to unplug the motor when I re-attach the handwheel, though strictly speaking it’s probably not necessary.

The next thing I do is use the grease syringe to dab some droplets of grease around the perimeter of the fiber gear. People often over-grease these things, but you really don’t need to go nuts with it.

Then I put a single drop of oil on the shaft.

Next I slide the handwheel on.

Replace the washer.

Then screw the stop-motion wheel in, all the way.

Don’t forget to tighten the set screw.

That’s it! Congratulations and enjoy your machine!

Back in business.