D12 electrical help?
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Category: Allis Chalmers
Forum Name: Farm Equipment
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URL: https://www.allischalmers.com/forum/forum_posts.asp?TID=171009
Printed Date: 30 Sep 2025 at 3:33pm
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Topic: D12 electrical help?
Posted By: Tracy Martin TN
Subject: D12 electrical help?
Date Posted: 10 May 2020 at 8:09pm
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Went to start a D12 in the shed today. Hadn't started it in 3 or 4 years. New battery, will not spark at plugs. This has a alternator, Delco one wire with plug. Noticed a resistor block near coil. Would not hit at all. I couldn't see a spark at points. Ran great when parked. What is most likely culprit? Thanks Tracy ------------- No greater gift than healthy grandkids! |
Replies:
Posted By: MACK
Date Posted: 10 May 2020 at 8:38pm
| Points need filed. MACK |
Posted By: Jim.ME
Date Posted: 10 May 2020 at 8:44pm
| Possible oxidized points. Fold a dollar bill up and use it to run between the point contact, that may do it. After 3 or 4 years don't be surprised if fuel system problems are next after you get spark. |
Posted By: Tracy Martin TN
Date Posted: 10 May 2020 at 9:52pm
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I looked at the points. They looked good. Took the carb off and cleaned it out first thing. I will check the points again. If they had fire to them, wouldn't they spark when opening them with a screwdriver? Thanks Tracy ------------- No greater gift than healthy grandkids! |
Posted By: steve(ill)
Date Posted: 10 May 2020 at 9:56pm
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clean the point contacts... pull one plug and check for spark when cranking.. If no spark, clean the point AGAIN.... if you have spark and it wont start, then look at the carb./ fuel. ------------- Like them all, but love the "B"s. |
Posted By: Tracy Martin TN
Date Posted: 10 May 2020 at 10:00pm
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Steve, it is getting fuel. No spark. I don't understand why it all of sudden quit sparking. If it ain't piss ants it is alligators. Been a hard spring here so far! Thanks Tracy ------------- No greater gift than healthy grandkids! |
Posted By: Gary
Date Posted: 11 May 2020 at 4:34am
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Did you try a jumper wire - Bat. to Coil ? |
Posted By: Jim.ME
Date Posted: 11 May 2020 at 5:37am
| Most things will oxidize over time when exposed to air, point contacts are no exception. The oxidization is thin and you might not see it, but it will prevent current flow. No current flowing, no spark when the flow is broken. |
Posted By: jaybmiller
Date Posted: 11 May 2020 at 6:06am
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Points are most likley oxidized.... Simple, old school test. Turn so points are open. Put voltmeter between points terminal and ground turn key on...should be 12 volts yes...turn engine to clsoe points, should be zero volts. if you didn't get 12 volts with points open, no power...open coil,open ballast resistor, busted wire, bad switch.... odds are real good points are lightly oxidized...400g paper,folded over ,to 'file' BOTH sides of points... ------------- 3 D-14s,A-C forklift, B-112 Kubota BX23S lil' TOOT( The Other Orange Tractor) Never burn your bridges, unless you can walk on water |
Posted By: Tracy Martin TN
Date Posted: 11 May 2020 at 9:08pm
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Filed points, weak spark at best, doesn't seem consistent . What is the points and condenser part numbers in a Neihoff or Echlin brand. Just want good ones, really doesn't matter brand. Thanks Tracy ------------- No greater gift than healthy grandkids! |
Posted By: Tracy Martin TN
Date Posted: 12 May 2020 at 7:21pm
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Well today was new points and condenser day, still the weakest spark I can barely see. What is most likely culprit.This tractor has alternator. It has a resistor right before the coil. What does the resistor do? Could I take it off and get a coil that does same thing? Any help appreciated. Tracy ------------- No greater gift than healthy grandkids! |
Posted By: steve(ill)
Date Posted: 12 May 2020 at 8:32pm
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If you have a resister before the coil, then it is probably an OLD 6 volt coil trying to work on 12 volts... THROW IT AWAY and buy a new 12 volt coil.... Any good brand is OK. ------------- Like them all, but love the "B"s. |
Posted By: Tracy Martin TN
Date Posted: 12 May 2020 at 8:42pm
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Steve, what does the resistor do? Tracy ------------- No greater gift than healthy grandkids! |
Posted By: Charlie175
Date Posted: 13 May 2020 at 5:48am
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My CA was like this the other day. Starting at the Dist. and working back I cleaned every connection. Fired up after that.
------------- Charlie '48 B, '51 CA, '56 WD45 '61 D17, '63 D12, '65 D10 , '68 One-Ninety XTD |
Posted By: jaybmiller
Date Posted: 13 May 2020 at 5:57am
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The resistor drop the 12 volts from the battery down to 6 volts for the coil. Points 'like' to have 4 amps of current through them to power the coil to make he big blue sparks. Electrical math...V/I=R, 6 volts/4 amps = 1.5 ohms. The resistor will be 1.5 ohms. Where it gets 'complicated' is when someone installs a 6 or 12 volt coil that doesn't need an external resistor, or someone 'removes' the original ballast resistor that was 'under the hood'. One test I do, is crank engine until points are open then put AMMETER between points connection on distributor and ground. With key 'on', you should see 4 amps +- . This confirms power is going from battery->key->resistor->coil. So if no spark, it'll be a points issue (corrosion or gap ). ------------- 3 D-14s,A-C forklift, B-112 Kubota BX23S lil' TOOT( The Other Orange Tractor) Never burn your bridges, unless you can walk on water |
Posted By: WF owner
Date Posted: 13 May 2020 at 6:30am
| If you are going to change to a 12 volt coil, make sure it is a 3 ohm coil (for a 4 cylinder tractor). |
Posted By: Steve in NJ
Date Posted: 13 May 2020 at 6:58am
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Trace, I answered your PM. Steve@B&B ------------- 39'RC, 43'WC, 48'B, 49'G, 50'WF, 65 Big 10, 67'B-110, 75'716H, 2-620's, & a Motorhead wife |
Posted By: Dusty MI
Date Posted: 13 May 2020 at 7:10am
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Back when cars went from 6 volt to 12 volt, they were set up to where the engine started using 12 volt to the ignition, then ran on 6 volt. Farm tractors with 12 volt systems start and run on 12 volt. So if you need to be careful when buying a new coil. Dusty ------------- 917 H, '48 G, '65 D-10 series III "Allis Express" |
Posted By: Tracy Martin TN
Date Posted: 13 May 2020 at 8:39am
Steve, great info for us electrically challenged. Much appreciated. Thanks Tracy ------------- No greater gift than healthy grandkids! |
Steve in NJ wrote:Posted By: Tracy Martin TN
Date Posted: 13 May 2020 at 7:53pm
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After today, I have decided that a person should have a license to wire on, work on, or weld on a tractor. Took the side panel off today, some people half ass everything! Tracy ------------- No greater gift than healthy grandkids! |
Posted By: Steve in NJ
Date Posted: 14 May 2020 at 6:23am
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LOL!! Oh, you'll be surprised what you find sometimes when it comes to the wiring! Trust me, its not a pretty sight! You wonder sometimes how they even ran! LOL! Steve@B&B ------------- 39'RC, 43'WC, 48'B, 49'G, 50'WF, 65 Big 10, 67'B-110, 75'716H, 2-620's, & a Motorhead wife |
Posted By: jaybmiller
Date Posted: 14 May 2020 at 6:46am
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The ONLY group worse than 'tractor bodgers' are commercial HVAC installers !!! No two ever wire tstats the same,even though a single cable of 5 conductors WILL do the job, I've seen THREE (3) cables of blk-wht pairs used to connect tstat to HVAC rooftop.... sigh.... ------------- 3 D-14s,A-C forklift, B-112 Kubota BX23S lil' TOOT( The Other Orange Tractor) Never burn your bridges, unless you can walk on water |
Posted By: Ted in NE-OH
Date Posted: 14 May 2020 at 2:36pm
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When not used the points can oxidize and get an invisible film which prevents conductivity, this happens to magnetos when they sit for a long time. ------------- CA, WD, C, 3 Bs, 2 Gs, WC, I-400, 914 |
Posted By: Brian Jasper co. Ia
Date Posted: 14 May 2020 at 9:48pm
------------- "Any man who thinks he can be happy and prosperous by letting the government take care of him better take a closer look at the American Indian." Henry Ford |
Posted By: Tracy Martin TN
Date Posted: 14 May 2020 at 10:57pm
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Brian, same goes for people that molest PTO shafts! Tracy ------------- No greater gift than healthy grandkids! |
Posted By: Steve in NJ
Date Posted: 15 May 2020 at 10:14am
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I think the funniest encounter I've had over the years wiring hotrods and Antique cars was the 34 Chevy Master Deluxe streetrod that I rewired. When I got under the dash to inspect things, the P.O. used bell wire to wire the underside of the dash. If you're not sure what bell wire is, it's the wire you wire your front door bell with. That was used pretty much throughout the whole dash. I took enough bell wire outta' that care to wire up dozen houses. It was workin'...... LOL! Steve@B&B ------------- 39'RC, 43'WC, 48'B, 49'G, 50'WF, 65 Big 10, 67'B-110, 75'716H, 2-620's, & a Motorhead wife |