Farmall A 12v conversion/ignition

isaacjr75

Member
Hello! My students and I (high school Ag teacher) are working on restoring a 1941 Farmall A (great story about this tractor I will show and tell in another post). When we received the tractor the magneto was damaged and the ignition system was poorly rigged, so we are starting basically from scratch to wire it. We are converting it to a 12 volt alternator system with an electronic ignition distributor. While we have the basic diagram included with the kit, I am looking for pictures of examples of how some have wired this type of set-up. I have a new complete restoration quality wiring harness that we'd like to use if possible (even if it needs to be slightly modified). Looking at different examples online, I see there are a ton on "pull" or "push" type set ups. I'd like to incorporate the On-off original switch, a solenoid and a key switch if possible. If you have any examples you could share, that would be greatly appreciated!


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Just a couple of comments, FWIW I have an "A" that came from the P.O. with a large Delco alternator like yours.

I plan on swapping it to a "mini alternator" which will tuck in much nicer next to the engine.

It's easy enough to install a new copper stud in the starter to allow the use of a a solenoid. Or, simply drill and tap the old stud for an 8-32 or 10-32 screw to hold a battery cable with an appropriate "eyelet" end to it. (Some scoff at this idea, but literally MILLIONS of Delco starters have been made with such a connection to the solenoid.)
<img src = "https://i.imgur.com/aJX859d.jpg">
It's opposite in that the connection made with the small screw is at the solenoid, rather then at the starter terminal, but the idea is the same, and it works.

I have another plan with the starter on mine, though, I have a flywheel ring gear from another tractor model that I believe will fit and allow the use of a much newer (10MT) Delco starter with a "shifted" starter drive to get away from the miserable "inertial starter drive" that was used "back in the day". (Not saying any more 'til I get a chance to verify it will fit and function.)

As to the keyed ignition switch, as long as you intend to got that route, I'd get one with a "start" position to work along with your starter solenoid conversion so a key is required to crank the tractor.

You mention a "push-pull" ignition switch, which obviously won't be needed with a keyed ignition switch, but if you DO intend to do that route, I'm sure you're aware that there's 2 versions, the one-terminal "push to kill" switch for use with a magneto and a two-terminal switch that operates in the same manner to supply power to a "Kettering" ignition system when the know is pulled "out".
 
Hello Isaac, welcome to YT! I will attach a link to some diagrams another poster has shared here. You should be able to use the heavier wire in the harness that originally went to the generator to attach to the back post on the alternator then you will need to splice it where the original regulator was and connect it up to the ammeter. The excite voltage to terminal 1 in the plug can be pulled from the coil feed upstream of the resistor if you are using one. This is the wire that needs a diode or small bulb placed in it to prevent alternator feed voltage from continuing to feed the ignition after the ignition switch is opened for shutdown. Great looking project so far, its great that you are keeping the students interested in old iron and part of our country?s past.
Bob s wiring diagrams
 
Thank you for the diagrams and advice! The kids definitely are enjoying the process! At some point, I'll post some start to finish pictures. Thanks again!
 
you can not use a solenoid with that button on the starter it is made for the original saddle sw mounted on top with a rod you push with your foot to start. You need a starter with a threaded stud if you want to use a solenoid. You are using the word"restore" wrong cause that means original. You are rebuilding it to newer standards. That starter is not for the A it is for a SA which uses a pull rod. Did you get the wiring harness for an Alt and Dist as they are different from the original A.
 
I understand what you're saying on the saddle mounted switch with the rod, however that's not the switch I'm referring to. I'm talking about the one with the black knob that you pull/push by hand (see attached picture). As far as restore or not...we're doing a TON of restoration I would think (we took it down to nuts and bolts...), all-be-it with some modifications and updates along the way...

Wiring harness, no, we have the style that was for the generator. At the time, we couldn't find one that was "original-looking" enough for an alternator. I was hoping we could make adjustments to what we had to make it work...

Thanks for the input!



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Not sure if I missed it reading through this thread but do you have the original starter that came with the A? The one with the small rod you push on with your foot to send power to the motor to start the motor.

If no one has a good picture or drawing I could take a couple pictures of the one on my BN.

If you have that starter just use that one. I know it's a "6 volt starter" so what it will not care if you send it 12 volts and actually I think it will work better and last longer running on 12 volts.

When volts drop the amps go up and that is what can kill any electric motor. So by putting higher volts to the motor will actually lower the amp load for the same amount of cranking power.

My BN has been working on 12 volts to the original 6 volt starter for something like 30 to 40 years and the only starter problem I had in all those years was a worn out Bendix gear assemble and for all I know it could have been the original 1947 Bendix gear!

As for wiring it's hard to suggest anything with out having a clear idea of what this ignition system needs for power. Do you have a schematic for it?

Same for the alternator. Would need to know if it is a "one wire" unit or "three wire" unit. My BN is set up with a Delco alternator that has one large wire for the output and two small wires connected to spade terminals on the internal regulator. Those small wires go to an pressure switch that turns on the alternator once engine oil pressure come up. I might be able to do a sketch of that part of the wiring if that is needed. It's been a few decades since I did it so I would have to double check it on the tractor first!
 
Maybe Rachel gingell could come visit your ag class. She seems to like Farmall A's since she has a buncha you tube videos with them. And she could straighten you out with any issues.
 
That's not an original switch, but it will work. If youre wanting to wire the key switch in as like a safety feature, just wire it inline of the switch to the coil.
 
I do have the original starter but it was in terrible shape and the rod was missing. It was rigged up with some strange push button start...I
would love some pictures if you have some, also to see how the original wiring harness was routed. As far as the alternator I have, it is a 1
wire alternator.

Thanks!
 
AS far as installing a starter solenoid to isolate the starter. Just follow the manufactures diagram. That's all I did for My IHC BN, since I live on a camp grounds and didn't want any from jumping on and accidentally starting the tractor. Through the switch all the rest of the lights run, so when switch is off no lights run. As far as the alternator I used a 12 volt Generator. makes the tractor look original and easier to wire.
Wm.
 
Well that sucks! Last night I wrote up a few paragraphs giving some ideas on wiring this project and thought I had posted them but now they are not showing up!

If I can get up the ambition and can remember any of what I wrote I'll try to write some of it a second time.
 

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