Alternator wiring Question
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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=146279
Printed Date: 14 Jul 2025 at 2:00am
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Topic: Alternator wiring Question
Posted By: GregLawlerMinn
Subject: Alternator wiring Question
Date Posted: 09 Jan 2018 at 8:00am
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Had a senior moment when installing a coil and EI module and did not document which wires went to which posts. Got the new coil and EI in and wired to the key switch and distributor then noticed a wire coming from the alternator that appeared to have been attached to the coil. I have installed several EI's and coils (both generator and alternator systems) and have never seen an alternator wire to a coil before. What terminal does it go on (Neg Grd system) and what purpose does it serve?
------------- What this country needs is more unemployed politicians-and lawyers. Currently have: 1 D14 and a D15S2. With new owners: 2Bs,9CAs,1WD,2 D12s,5D14s,3D15S2s, 2D17SIVs,D17D,1D19D;1 Unstyled WC |
Replies:
Posted By: jaybmiller
Date Posted: 09 Jan 2018 at 8:10am
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Um... what make/model alternator and where's the wire ON the alt? Jay ------------- 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: GregLawlerMinn
Date Posted: 09 Jan 2018 at 8:29am
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Eichlein Mexico is one the alternator. There are 3 wires attached to it, one apparently went to the coil. ------------- What this country needs is more unemployed politicians-and lawyers. Currently have: 1 D14 and a D15S2. With new owners: 2Bs,9CAs,1WD,2 D12s,5D14s,3D15S2s, 2D17SIVs,D17D,1D19D;1 Unstyled WC |
Posted By: Sugarmaker
Date Posted: 09 Jan 2018 at 8:37am
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Greg, I dont think any of those go directly to the coil. I always have a fit with this stuff too. hang in there the experts will be along. Lots of ways to wire these up. The wire going to the coil should be coming off of a switch in the dash which gets power from the battery. Regards, Chris ------------- D17 1958 (NFE), WD45 1954 (NFE), WD 1952 (NFE), WD 1950 (WFE), Allis F-40 forklift, Allis CA, Allis D14, Ford Jubilee, Many IH Cub Cadets, 32 Ford Dump, 65 Comet. |
Posted By: DougS
Date Posted: 09 Jan 2018 at 9:08am
| It *might* be the exciter wire and it might work that way because the alternator might have an internal resistor on this wire. There are a lot of ‘mights’ involved. Does this wire go to a terminal tagged with an I? In any case it would be best to connect this wire at the ignition switch. |
Posted By: GregLawlerMinn
Date Posted: 09 Jan 2018 at 9:20am
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There was a resistor block between the switch and coil terminal. Should I connect the loose wire to the switch side term...or not connect it at all? ------------- What this country needs is more unemployed politicians-and lawyers. Currently have: 1 D14 and a D15S2. With new owners: 2Bs,9CAs,1WD,2 D12s,5D14s,3D15S2s, 2D17SIVs,D17D,1D19D;1 Unstyled WC |
Posted By: IBWD MIke
Date Posted: 09 Jan 2018 at 9:45am
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I find, (for me at least), it's handy to have a spare tractor with working system around when working on anything electrical! I sometimes go so far as to park the working one close to the one being worked on to save steps. |
Posted By: Gerald J.
Date Posted: 09 Jan 2018 at 10:13am
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I don't know about the Eichlein Mexico alternator but Delco SI series there are three wires. A big one (8 gauge for more than 30 amps, 6 gauge for 50 amps) That goes to the positive post of the ammeter for battery charging. Negative post of the ammeter goes to the positive battery post, often via the starter cable. One of the other wires connects somewhere for a voltage sample. Simplest but poorest is to the output post of the alternator, better would be close to the battery. The third wire excites the alternator regulator so it charges without having to be spun fast like a one wire alternator. The exciter wire feeds back 12 volts to the ignition circuit so generally is connected to the ignition switch through a lamp (alternator lamp), a resistor, or a diode to keep if from supplying enough power to the ignition system to keep ignition going with the ignition switch off. It shouldn't be connected to the coil with a resistor between the coil and the ignition switch. Normally the + primary terminal on the ignition coil goes to the ignition switch and the - terminal goes to the points or the electronic ignition, but I'm sure different electronic ignition systems may be wired differently. Gerald J. |
Posted By: steve(ill)
Date Posted: 09 Jan 2018 at 12:24pm
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Read what Gerald said and look below... ------------- Like them all, but love the "B"s. |
Posted By: steve(ill)
Date Posted: 09 Jan 2018 at 12:28pm
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Here is a different drawing with the alternator terminals marked.... and the 10 ohm resister takes the place of the idiot light / diode.......... and shows you MIGHT have a ballast resistor on the coil of your OLD 6 volt unit .......... not needed on 12 volt.
------------- Like them all, but love the "B"s. |
Posted By: Gerald J.
Date Posted: 09 Jan 2018 at 6:59pm
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Ballast resistors were very rare in 6 volt systems. More common on 12 volt systems using a vintage 6 volt coil. The only place I've ever heard of a ballast resistor being used in a 6 volt ignitions system were some vintage Dodge cars with very high speed engines. A ballast resistor in series with a coil generally allows the current to rise faster when the points are closed than with a coil primary winding rated for the voltage. There's no 6 volt tractor engine running over 2200 RPM or with more than 6 cylinders so there's no need for a 3 volt coil and a ballast resistor like the Dodge V-8 turning over 5000 RPM, maybe as much as 8000 RPM. Gerald J. |