[AT] '49 A Wico Magneto

Tue May 12 18:33:19 PDT 2020

Steve, 

To me it sounds like the coil is good, but again I’m not totally familiar with how your coil generates the required energy since you need a rotating field to create a field in the coil. There should be an armature driven off the timing gear that generates that field, it should be mounted under the coil. With essentially two coils, I don’t quite understand how both coils work together, possibly actually a center tapped coil, with the center button being the center tap. But again why a center tapped coil? The bar you referenced just helps to generate a stronger field, just as in a transformer.

Rather than keep guessing on what might be your problem, and having you chasing this and that, I did a little searching on-line and found two items. One is the actual manual for your magneto, which I believe is what you already have. The other can be found through this link:

http://lindemanarchives.com/wp-content/uploads/2013/08/Magneto-Restoration002.pdf

This document shows how to test your magneto without the use of the special tester. Take a look at it and see if it helps. I didn’t read through the whole thing, but it looks like it has potential to solve your problem.

Carl
----- Original Message -----
From: STEVE ALLEN <steveallen855 at centurytel.net>
To: at at lists.antique-tractor.com
Sent: Tue, 12 May 2020 20:11:22 -0400 (EDT)
Subject: Re: [AT] '49 A Wico Magneto

Brad,  Thank you for that link:  I will try that test.

Carl (and everyone):

OK, on a Wico X magneto, the coil is actually a 2-part unit.  The outer coil and the inner core.  The inner core is an iron bar that slips through the center of the coil and is clamped to the mag case.  The outer coil is sealed in plastic.  One end is covered in a poured resin; out of that end come 2 wires.  One is bare along most of its length and is grounded to the mag case on one of the clamp screws.  The other is insulated along its whole length, and the ring terminal on its end is the wire screwed to the points, specifically the spring arm on the moveable point.  On the front side of the coil, a metal contact button sticks out.  This button contacts the spring arm on the cap which also contacts the center button on the rotor.

Now, I have used the meter to establish the following two facts:
1)  The two wires have COMPLETE continuity between them:  the 1K scale on the meter reads 0--ZERO--Ohms.  No resistance.
2)  The contact button has SOME continuity with the two wires:  the 1K scale reads 6--i.e. 6000 Ohms.  Some resistance.

If I understand the test you suggested below, its purpose is to establish that the wire to the points is intact along its length and connected to the coil.  I believe that the fact there is 0 Ohms resistance between the two wires coming out of the coil demonstrates that it is intact and connected.  (If my assumption is hasty, let me know!)

The Service Manual offers tests to be performed on the bench on expensive and proprietary equipment, most of which probably got recycled decades ago ;-)  But, as I understand what it says, a coil is either good or bad--no in-between.

So, let me ask for verification of two statements:
A)  A coil is either good or bad without a partial functioning condition.
B)  A Wico mag coil should have 0 Ohms (full continuity, no resistance) between the two wires emerging from its end BUT about 6000 Ohms (some resistance but still continuity) between either of those wires and the contact button on its side.

I am no EE, and my electricity shop is MANY years behind me!

I thank everyone again for reading my missives and any and all advice, suggestions, and other help!

The "original" Steve Allen

----- Original Message -----
Message: 7
Date: Mon, 11 May 2020 23:30:40 -0400 (EDT)
From: szabelski at wildblue.net
To: Antique Tractor Email Discussion Group
	<at at lists.antique-tractor.com>
Subject: Re: [AT] EVENING UPDATE
Message-ID:
	<1839256707.22813490.1589254240661.JavaMail.zimbra at wildblue.net>
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OK, here is what I?ve seen on the magneto for my Cub. There should be a small reading from the coil wire to the magneto case when connected to the screw. I?ve read that it?s correct, but don?t quite understand why since this would indicate a grounded circuit to me. I believe it has something to do with the points and condenser that are also attached to the screw and there is a bleed circuit that doesn?t affect normal operation.  I?ve measured from the screw to the case with everything disconnected and there is no continuity, it only shows up when everything is connected.

As far as no continuity between the coil wire and the center contact, there should be a reading This is nothing more than a very long wire wound around a metal core. No reading would indicate an open circuit which means there?s a break in the circuit. Now the break could be in the coil itself. OR....

The wire from the screw is disconnected from the coil itself, which you may be able to fix with a little solder. OR...

There is a break in the wire itself, which again you should be able to fix.

Take a probe from your meter and push it into the wire right at the point were it enters the coil. Measure from there to the end of the pigtail wire. Continuity means good wire. No continuity means break in the wire, or your not making good contact were you inserted the probe. You may want to strip a little insulation off of the wire at the coil to ensure you get a good contact. You can always patch it with some heat shrink or RTV. Also, you may be able to see the solder joint where the pigtail connects to the coil. If so put the probe there.

Next check from were you inserted the probe to the center contact. No continuity means a break in the coil, which is not repairable, or the pigtail wire is disconnected from the coil. You may be able to peel back some of the coil insulation to get to where the wire attaches, and if disconnected, resolder it. You won?t damage the coil as long as you don?t knick any of the coil wire. If you have to pull a little of the coil wire out to solder, that?s OK, just carefully scrape the varnish off of the wire before you solder.

One more thing would be that the center contact is not connected to the other end of the coil, but I would doubt that since it?s essentially molded into the coil body and I don?t see how it would become disconnected without the coil  possibly being severely mishandled or dropped.

I realize that my magneto and your magneto are slightly different designs, but their basic operation should be the same.

Good luck.

Carl
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