Farmall A 1941 Magneto Conversion

Hello. I have an almost restored 1941 Farmall A. I want to do a simple conversion on the magnetio setup to a 12V coil, points, condenser setup. The mag has lost its spark. I also need to time the gears in the mag. I do have a new Delco Remy D512 coil. Do I need a ballast resistor in this setup? I see Napa has the 905 coil with an internal resistor. If one is needed I would rather have the internal type. Less mess. Then I need to know about correct points and condenser if needed. Does one use the stock points or something else. And do I add a condenser and if so what type? Watched a few videos where a condenser is installed where the grounding wire is in the magneto. Course disconnecting the internal coil of the mag to the points. But I really need part numbers to get things right. I have added a 12V system with one wire alternator and starter to the tractor. Cranking by hand is fun but pulling the starting rod is way nicer. Thanks for helping. Curt
 

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Hello 63merc, welcome to YT! Are you checking the spark out of the coil of the magneto or to the individual spark plug wires? If you are checking it at the cap towers if your rotor gears are out of time that may cause you to have no spark out of the cap. You should still have spark out of the coil. From what I find on line the D512 coil is 1.8 ohms, that’s a 6 volt coil so it will require a resistor. If you use that NAPA coil for 12 volts you won’t need a resistor. Just get a condenser for regular battery ignition A, NAPA seems to have fair quality ones. You can use the points you have if they are good. I don’t know the part number if you need to replace them. Maybe someone will reply back with the numbers. By the way there is not really an internal resistor coil. The windings in the coil are just designed to by the length and turns to provide proper resistance. You A is very nice!
 
Nice tractor!

"Watched a few videos where a condenser is installed where the grounding wire is in the magneto."

Yes, that's where the factory "hid" the condenser.

I don't know, offhand, what the capacitance value is, but, as a rule of thumb, battery ignition system typically use condensers with 1.5X to 2X the microfarad capacity of magneto capacitors.

However, the existing condenser will work, but spark MAY not be as "hot"as it it "matches" the coil and point pitting will occur over time if the value is too far "off".

One thing you can do is pick a coil that's listed as a replacement for a certain vehicle or tractor and use a condenser listed for the same application.

4umw5xx.jpeg


Coil mounting brackets typically have a mounting area for RF suppression condensers, you can mount your new condenser there and eliminate the one in the magneto.

As to timing the magneto's rotor, look on Pages 51 and 52 in the Blue Ribbon Service Manual linked below.

BTW, your OEM IH magneto is an "H-4".

https://farmallcub.com/rudi_cub/www.cleancomputes.com/Cub/Blue Ribbon Service Manuals/GSS-5035 Service Manual Magnetos/GSS-5035 Service Manual Magnetos.htm


One other thing... I notice the coil cover on your mag is painted.

Conventional wisdom is that such things shouldn't be painted, as some paints are conductive and will "bleed off" some spark energy.

Others will argue that's NOT true and brag about their nicely painted coil covers and distributor caps, LOL!
 
I converted my
A last year to a distributor got all the parts from Steiner in Michigan then ordered the Pertronix conversion kit. Worked very well. Now the coil just has to have an internal resistor or if it's a 12 volt coil an external resistor.
 
Is the Pertronix an electrical conversion?
Pertronix is a unit that converts a points distributor to an electronic ignition. I don’t think they have anything to convert a magneto. Not sure if you know this but the proposal you are making to convert your magneto to a battery ignition is really considered a “short cut” approach.
 
So you can fix the mag then. Tell me about it please.
You can have a “Private Message” with Teddy to exchange emails or phone numbers out of the eye of the web. Click his username above his post and click “Start Conversation.” On his end a number will appear in his message box icon on the top that looks like a “letter or mail” he will click that to access your message and you as well to receive his reply.
 
A great manual on ihc magnetos is the blue ribbon manual . Highly recommend it . I got mine off of eBay . Goes through theory ,earlly magneto’s, and h4 which you have and j4 cubs ,Wico .
I had a cap fail, so consider that troubleshooting.
 
Well now I am considering the costs of conversion to restoration of this magneto I have already dropped SO much into this restoration. Course reliability is a consideration as well.
 
Got it yesterday, a day late. Had spark but I took it all apart to charge the magnet. Points were iffy so I put in a new set. Run it with a cordless drill at normal speed before I put the impulse on & it throws a spark almost 3/4 inch long. One of the hottest I have seen! May get it back in the mail today. Thanks, Don.
 
Got it yesterday, a day late. Had spark but I took it all apart to charge the magnet. Points were iffy so I put in a new set. Run it with a cordless drill at normal speed before I put the impulse on & it throws a spark almost 3/4 inch long. One of the hottest I have seen! May get it back in the mail today. Thanks, Don.
Be sure the O.P. understands that the terminal on the mag is for the "kill switch"/grounding only and to NEVER apply battery power to it.
 

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