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Farmall M going from 6 volt generator to 12 volt generator

R

Robert in KY

New User
I'm taking my Farmall M and going from 6 volt generator to 12 volt generator. I feel like I should know this but since I'm going from positive ground to a negative ground, am I just switching the A and F on the generator and keeping the regulator the same? Just doesn't seem right and the more I look at it the more I doubt it. Someone slap me or tell me what is what here.
 
Nope.
The regulator needs to be 12v. The regulator still needs to be connected Arm on gen to Arm (or Gen) on the regulator. The Field (F) terminal needs to be connected to te F on the Gen. If the regulator is designed for Positive ground, it will either not work, or not work for long on negative ground. Some regulators (US made) can be used on + ground or negative ground. Make sure before purchase.
The only changes needed are:
1) Battery reversed
2) amp gauge reversed
3) Light bulbs changed
4) New generator polarized before starting the engine (with all things connected, and the key off, jump a hot wire to the generator ARM terminal, it will spark, hold for one second, then remove (more is not better)). This places magnetism in the field"s iron poles so it charges in the correct polarity. Jim
 
Also, if it has a distributor check the + and - connections on the coil. Positive ground + to side of distributor, Negative ground - to side of distributor.

No changes with magneto as it has no connections to the battery system.
 
Sparky Jim has you well covered on wiring etc. I will just add that just because you're going from a 6 to a 12 volt Generator THERES NO ACTUAL NEED TO CHANGE TO NEGATIVE GROUND although no harm either. Its just that if you stay at Pos ground you don't have to swap ammeter or ignition coil leads. If its a coil distributor ignition however (not a Mag) you need to EITHER get a 12 volt coil or else add a series voltage dropping (12 down to 6) ballast resistor if you use the old 6 volt coil. As Jim noted your new 12 volt voltage regulator needs to be suitable fro whichever ground you choose. One advantage of going to Neg ground is that a lot of 12 volt tractors are configured that way and it makes for easier jumping for an inexperienced operator. She will crank over much faster if you go to 12 volts.

We may tell you what is what but we rarely slap folks on here lol

John T
 
"What is what" is that you aren't getting away from your headache! It isn't just 6volt regulators that are junk now days, they all are. I tried and tried to get 12 volt regulators to work on a couple of tractors. Wasted lots of dough on regulators that would work a week. Finally paid $35 for an alternator and haven't touched it since. There's two old machines I don't have to worry about now.

Funny thing is, the damage is done. I watch that amp guage like a hawk every time I start them even though I know there won't be a problem.
 
Robert,
I went the same route you are contemplating. Used a MD generator on my SM when I restored it. I kept the ground positive so all my wiring is still IAW the original wiring diagram. I scrapped the 6 volt coil and went with 12V. The tractor starts and runs great. The 12V genny keeps the battery fully charged and has no issue when all lights are being used. I would suggest you go with a American made regulator. Brillman sells them. I have had a brillman on my H for over 10 years and now my SM and neither have had issues.

r/

Pete in NC
 
Thanks for the advise. I have a mag so I'm covered on the mag distro side. I know that I'm rolling the dice by going with a 12 volt gen/regulator but you can't beat free. Since I have only had to buy a 12 volt regulator I don't see trying this too much of a loss. Guess I'll see what happens.
 
I'm also thinking of staying with a positive ground. Without an alt there really is no reason to reverse things. All I would be doing is changing the voltage. Bottom line is, I was over thinking this way too much. Change the generator and swap the lights bulbs out. Simple. I guess this is the problem not learning basic auto mechanics on old classic cars with simple charging systems. I was kicking my own tail for no real reason.
 
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