12 volt Conversion WITH Magneto Farmall A HELP

[used red MN]

Here is a wiring diagram for what you are doing. It is for a Super H, 6 volt positive ground but it should be the same for what you are doing. It is for a battery ignition so ignore then ignition wiring coming off the fuse. If it’s not hopefully some will chime in. Super H wiring diagram
You say “the wiring is all new” What is under the tape on the terminal ends of the wire. If they are just crimped go to everyone and tug on it good like your going to pull it out of the terminal. If it yanks out the connection wasn’t good enough. If it doesn’t pull out push it in, if you feel it move any in the connector, the connection is not good enough. Crimped, then soldered on and shrink tubed is a reliable connection you can trust for reliable service.
What kind of meter you using? The electrical noise from the brushes on the commutator and probably even from the mag hamper the ability of many cheap meters to give accurate readings. Got an old 12 volt headlight laying around? See if it will light up wired to the terminal on the ammeter opposite of the one connected to the battery. If it lights up and the ammeter shows discharge there is a 95% chance it is good.
I haven’t researched your ammeter check with a AA battery but I would guess it will only twitch the needle slightly.

 

[Jim Becker]

How many amps can your ammeter display? If it is a 40 or 60 amp meter, the tiny current required to maintain a fully charged battery may be difficult or impossible to see on the meter. Measure the voltage directly on the posts of the battery. Then start the engine, rev it pretty well up, and measure the voltage at the battery again. If the second reading is higher than the first, it is charging.