WD Magneto Question
Printed From: Unofficial Allis
Category: Allis Chalmers
Forum Name: Farm Equipment
Forum Description: everything about Allis-Chalmers farm equipment
URL: https://www.allischalmers.com/forum/forum_posts.asp?TID=175848
Printed Date: 25 Aug 2025 at 9:21am
Software Version: Web Wiz Forums 11.10 - http://www.webwizforums.com
Topic: WD Magneto Question
Posted By: PollackPete
Subject: WD Magneto Question
Date Posted: 09 Nov 2020 at 2:36pm
| Hi.New here,but not new to old tractors.Recently bought a non running 1950 Allis Chalmers WD with a Fairbanks Morse X4B3 magneto.Had no spark when I bought the tractor.Since buying it,I have put in new points and condenser,new coil,new impulse coupling,new rotor,and gasket set.Still have no spark.Today,I checked for continuity between the kill lug on the mag and mag case.I do have continunity there,which I believe,shorts out the ignition.Pulled the new coil out of the mag and checked between the primary wire and the coil mounting lugs and also have continunity.If I'm thinking correctly,the coil should not show continunity here.Am I right?If so,I have a defective coil.Help me please.I'm pulling out what little hair I have left.Thanks for any and all info. |
Replies:
Posted By: PaulB
Date Posted: 09 Nov 2020 at 7:47pm
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If you send the magneto to one of the rebuilders, they can fix whatever the problem is, test it and guarantee it. I go to John Brillman for anything electrical related. http://www.brillman.com" rel="nofollow - www.brillman.com ------------- If it was fun to pull in LOW gear, I could have a John Deere. Real pullers don't have speed limits. If you can't make it GO... make it SHINY |
Posted By: allischalmerguy
Date Posted: 09 Nov 2020 at 9:44pm
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You probably watched this already. But non the less interesting. https://youtu.be/2fmnP700qXc" rel="nofollow - click here to see video ------------- It is great being a disciple of Jesus! 1950 WD, 1957 D17...retired in Iowa, |
Posted By: steve(ill)
Date Posted: 09 Nov 2020 at 9:55pm
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https://www.yesterdaystractors.com/cgi-bin/viewit.cgi?bd=jd&th=205166%20" rel="nofollow - https://www.yesterdaystractors.com/cgi-bin/viewit.cgi?bd=jd&th=205166
------------- Like them all, but love the "B"s. |
Posted By: Ted J
Date Posted: 10 Nov 2020 at 4:43pm
------------- "Allis-Express" 19?? WC / 1941 C / 1952 CA / 1956 WD45 / 1957 WD45 / 1958 D-17 |
allischalmerguy wrote:Posted By: allischalmerguy
Date Posted: 10 Nov 2020 at 7:58pm
Ted well probably because they are not mine nor yours! Ha Ha! Mike ------------- It is great being a disciple of Jesus! 1950 WD, 1957 D17...retired in Iowa, |
Posted By: Matt (Jordan,MN)
Date Posted: 11 Nov 2020 at 2:03am
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If your wire from the kill switch is not hooked up to the points and you show continuity between the wire and mag housing then your kill switch is grounded and most likely your problem. You should have continuity between the wire and core bar in the coil. This is one of the tests to do to check resistance in the coils primary circuit. Your meter should show about .5 ohms. I’m guessing that your kill switch is the problem. ------------- Owner of Matt Scott LLC Specializing in NOS and used Allis Chalmers tractor & implement parts & liturature and Magneto Repair http://www.mattscottllc.com/ |
Posted By: Newwood
Date Posted: 16 Nov 2020 at 4:11pm
| well, 2 weeks ago I happened to do a continuity test between the magneto post and frame on mine (with the wire disconnected from the kill switch and ungrounded) and was dumbfounded to find positive continuity. Grounding the wire against the frame kills the engine and when the wire isn't grounded the engine starts and runs fine. I'm totally mystified by how this works (unless it's some resistance level not detected by a simple continuity tester), but my conclusion is the fact that you found continuity between the post and frame doesn't indicate that you have a problem (although the mystery of why this can be true remains for brighter bulbs than me to explain) |
Posted By: steve(ill)
Date Posted: 16 Nov 2020 at 4:56pm
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the coil has a HOT wire to the point... the coil CORE is the other end of the wire and it is grounded... I would guess your measuring you kill wire thru the coil to ground. ------------- Like them all, but love the "B"s. |
Posted By: Newwood
Date Posted: 18 Nov 2020 at 4:53pm
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Steve well, in my case the kill wire was removed, so I was measuring from the post on the magneto housing (where the kill wire attaches) to various points on the frame (or on to the magneto housing -- it's all metal and connected so all in continuity). I think there is only one wire coming from within the magneto coil (this is all inside the magneto) and (at least from what I can tell from photos) that single wire goes to that post on the inside the magneto. But is that post somehow electrically insulated from the housing of the magneto which it goes through (from inside to outside the magneto)? The exploded diagrams never seem to show this and it looks for all the world to me that the post is in contact with the housing--and continuity testing supports that conclusion--but then the whole kill circuit would make no sense (why would a wire from the post to the frame kill it if the post is already in continuity with the frame?). If the post is somehow insulated from the housing, and the continuity is some (high resistance?) pathway through the coil, then perhaps it's just that the exploded diagrams don't show the parts that are insulating the post from the housing and a resistance test would reveal all. Hummm, inquiring minds want to know! jack
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