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Farmall & IHC Tractors Discussion Forum
:

Farmall M Electrical Confusion

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FarmallMOwner1

12-09-2016 03:08:42




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I've posted a few times about my old Farmall M tractor. The tractor was left in a field by the previous owner of my house, where it had been sitting for 20 years. I've made it my mission to get it running since it was free to start with.
I've managed to get her fired up and running, but she clearly has some form of electrical issue. IF the battery is completely charged, she'll run for about 20 minutes then she'll die. The battery is usually dead after that time. I'm assuming my generator isn't working, or I need a new battery. I've looked at many wiring diagrams, but I can't seem to find one which matches my system.
The tractor has some clear modifications to the electrical system. It's a 1940-ish farmall which has been converted to use a 12V battery. It has the push button starter switch which directly connects the battery to the starter moter.

I've posted2 photos of the generator side of the system. I have no idea what the white box is in the system. I also don't know what the white box is attached to. I know the generator is on top and the distributor is on bottom.
The white wire, which drops to the bottom of the image, is unattached on the one side. It goes back into the taped-up wires going towards the box by the seat, but it doesn't come out the other side.

I would appreciate if I could get some help at least labeling all of the unkown parts. Knowing what a part is called really helps when searching for a solution.
I hope to draw out the wiring this weekend.
third party image third party image

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charlieu

12-11-2016 17:30:10




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 Re: Farmall M Electrical Confusion in reply to FarmallMOwner1, 12-09-2016 03:08:42  
M Owner, When you looked at my wiring diagram you missed the "diode plug" that is plugged into the alternator to excite it and get it started to charging and it also prevents it from back feeding preventing the engine from shutting off when you push in the ignition switch. Here is a picture of the diode plug that I have for sale. third party image

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FarmallMOwner1

12-10-2016 19:08:50




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 Re: Farmall M Electrical Confusion in reply to FarmallMOwner1, 12-09-2016 03:08:42  
I also forgot to mention that I bought and installed a new coil. The old coil had about 30 ohms resistance between the 2 side terminals. From what I read online, there should only be about 1 ohm resistance. Is it possible that a new coil somehow messed up my timing?



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FarmallMOwner1

12-10-2016 19:06:22




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 Re: Farmall M Electrical Confusion in reply to FarmallMOwner1, 12-09-2016 03:08:42  
Thank you everybody. Knowing what components I'm looking at helped narrow down the problems. So far, I've identified the following:

1. According the charliesrepair.com web page, I was missing the wire between the alternator and the resistor. I added that wire back in.

2. I wasn't able to find any shorts in the system, so I decided to take a second look at the battery. Turns out the battery was bad, so I exchanged it for a new battery.
The tractor now fires up pretty nicely. However, it now backfires and shoots flames out of the exhaust every minute or so and it seems to be lacking power. I'll check the spark plugs tomorrow to make sure I have a good, strong spark. Otherwise I'll try tuning the carb to see if that helps.

I did notice that, since adding the wire from the alternator to the resistor, the tractor will keep running if I turn the ignition switch off and leave it out of gear. It only stops when I put it back into gear. Is this normal? Is this a sign that I've got something wrong?

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Janicholson

12-11-2016 13:46:18




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 Re: Farmall M Electrical Confusion in reply to FarmallMOwner1, 12-10-2016 19:06:22  
The wire from the #1 Alternator spade terminal should go to one of three choices before going to the resistor (on the ignition switch side of the resistor) All options are through the device, not to ground. One option is a side marker light bulb (not LED). Option 2 is a 10 ohm 10 watt resistor. The third is a 3 amp 150piv diode with the diode band toward the alternator. These devices conduct enough battery voltage to excite the alternator, but cannot support the alternator's voltage regulator supplying the engine with spark. Which is why it is continuing to run when shut off. Jim

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farmboy48

12-09-2016 21:53:29




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 Re: Farmall M Electrical Confusion in reply to FarmallMOwner1, 12-09-2016 03:08:42  
charlieu, I don't have number right now, tractor is snowed in at the farm. It seems to be ok with no discharge, just seems the output is a little low. Will have to look at it in the spring when snow is gone. I saved your website for further information.

Dick ND



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charlieu

12-09-2016 11:13:01




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 Re: Farmall M Electrical Confusion in reply to FarmallMOwner1, 12-09-2016 03:08:42  
Yes & No some Mitsubishi and Hitachi alternator are made differently, and are wired externally differently. Do you have the number of the Mitsubishi alt that you installed on your M?

If your engine shuts off and the battery does not go dead I would say that it's wired OK.



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old

12-09-2016 08:52:16




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 Re: Farmall M Electrical Confusion in reply to FarmallMOwner1, 12-09-2016 03:08:42  
As said the white box thing is a ballast resister to drop voltage for the stock 6 volt coil

As for the battery drain a good battery can/will run a tractor for many many hours. Matter of fact I I have a ford tractor that I ran with out a working charging system for years and all I did was once in a while charge the battery but even then it ran that way with out being charged for a month or more.

So tha tall said you have a major short some place. As for wiring all you need it a simple on/off switch for the ignition and the wires for the charging system place the start circuit. I would unhook the alternator wiring and see if it will run a lot longer with it unhooked. If it does run a long time then you problem is the alternator

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farmboy48

12-09-2016 08:44:14




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 Re: Farmall M Electrical Confusion in reply to FarmallMOwner1, 12-09-2016 03:08:42  
Charlie, I put a Mitsubishi alt on an M a while ago, assume it wires the same as Hitachi?? I installed bulb in circuit to prevent draining battery.

Dick ND



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charlieu

12-09-2016 05:59:34




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 Re: Farmall M Electrical Confusion in reply to FarmallMOwner1, 12-09-2016 03:08:42  
Maybe I can help, Take a look at my website (charliesrepair.com) and click on wiring diagrams. You can then take a look at Farmall M, Delco alternator with 6 volt coil. I have made a bunch of wiring diagrams for these older tractors. I hope this helps. Charlie U



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BarnyardEngineering

12-09-2016 04:55:28




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 Re: Farmall M Electrical Confusion in reply to FarmallMOwner1, 12-09-2016 03:08:42  
Your tractor should run for several hours at least on a weak battery.

To kill a battery that's capable of starting the tractor in only 20 minutes, you have a dead short somewhere. Some wire has had its insulation rubbed off and is laying against the tractor frame.

An M's wiring is dead simple, there is not a lot to it, so not much to check. Inspect all the wiring and look for bare spots.

With a short bad enough to drain the battery in 20 minutes, you should be able to find a burned area in the wiring pretty easily.

When you find the spot, you can temporarily repair it by wrapping the wire with electrical tape.

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John M

12-09-2016 04:46:08




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 Re: Farmall M Electrical Confusion in reply to FarmallMOwner1, 12-09-2016 03:08:42  
Your generator is an alternater, the white thing is the resistor for the coil, which is most likely 6 volt. (Resistor drops the voltage down from 12 volts.) The coil is what is sitting on top of and is attached to. You have some other problem if its killing a battery after only running for 20 minutes.



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Lpakiz Larry

12-09-2016 15:52:38




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 Re: Farmall M Electrical Confusion in reply to John M, 12-09-2016 04:46:08  
Has anyone considered that the jury-rigged starter system might be causing the starter motor to continue to spin while the tractor runs? It seems likely that it could discharge a good battery in about 20 minutes.



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