Farmall Super H 12v Batt only

My grandad has a Farmall Super H and he use a 12v Batt in it. None of the rest of the tractor has been converted to 12v and it still has the original generator on it. I know the voltage regulator, Coil, and Distributor need to run on 6V instead of 12 so I was trying to wire it so that they would.

What i did was take the wire running from the started to the AMMETER and place a resistor there. In my mind that should make everything past that run at the desired voltage. Thing is if i use my volt tester to check the voltage at the regulator I'm still seeing 12v. So what am i doing wrong?

The 12v in the 6v system has probably fried the system.Your gonna get 12 v all over.IMHO.Strip the old elec system ,rewire,install 12v alternator.Or have gen/reg checked(bet they're burned up)Renew them and go back to 6v battery.I am NOT an electrictian,so take this with a 'grain of salt'.

> So what am i doing wrong?

Pretty much everything. A resistor (how did you decide what value to use?) is not a voltage converter. Either do as DeltaRed says and convert fully back to 6V (repairing any damage you did) or read up on how to convert to 12V.

I didnt make the batt change im just trying to fix it now that it wont run correctly. I runs like it should for about 10 minutes then the coil gets to hot to touch and it starts running horible, I agree that the Regulator and generator are probaly fried and that it should be converted to altenator, but Trying to convince my grandfater to do it has been impossible.

So pretty much i have 2 options. Put a 6v Batt back in it OR convert the whole thing to 12v, is this correct?

You can get it operational pretty cheap and easy with a partial 12v conversion. You would just need to charge the 12v battery with a charger occasionally till you can get an alternator installed.

My Farmall SC lasts a couple months of very occasional running before I need to charge the battery. Eventually I will get an alternator on it.

If you want to go this route:

Remove all wire and rewire from battery + to switch, from switch to + side of new 12v coil, (buy one with no external resistor required). From - side of coil to distributor. Battery: negative to frame and positive to starter.

This is a quick wire job that will get the tractor electrically functional and allow you diagnose other issues.

I'd recommend a new 12v coil, +-$20., as I think old one has failed.

You.re running a 6v coil on 12v,thats why its gets hot.When it quits/runs like crap,that means your coil is toast-your points are probably burnt,also.Replace it with a 12v internal resisted coil.

You.re running a 6v coil on 12v,thats why its gets hot.When it quits/runs like crap,that means your coil is toast-your points are probably burnt,also.Replace it with a 12v internal resisted coil.

Thanks for the info. As far as the resistor it came from NAPA and what was asked for was a resistor to run a 6v Distributor off of a 12v batt, at least that is what i was told.

He has a Farmall A tractor also that was converted to 12v, probaly by some one else seeing haw the H was done, and it works great. So I know how to do a full conversion with no problem. Also seeing how there is a guide on her to follow to do it for a Super M which is pretty much the same thing electricly Im all set with that.

I was just trying to get the thing running with what we had on hand and from the info gathered from these posts I think I have a pretty good Idea of what NEEDS to be done to fix it.

I know we have a 12v coil or two laying around off of old cars so for now i think Ill just switch out the coil then place the resistor between the coil and the distributor and for go battery charging. That should at least allow me to get it "running" correctly. Then I will go take the alt bracket off my Uncles Super M and use it as a guide to Fab one for he Super H and go from there.

I thank you guys/girls for your assistance as I was at a loss on how to work on these older engines. Ive never owned a car with a distributor / Coil setup and certainly not one that ran on 6v so I was at a loss.

If it now has a 12 volt battery but its still the old 6 volt coil, you can add an external series voltage dropping (12 to 6) series ballast resistor (typical values in the 1.2 to 2 ohms)after the ign switch before and ahead of the coil so it drops 6 volts leaving 6 on the coil as a 6 volt coil was designed for, orrrrrrr toss the coil and use a 12 volt rated coil that requires no ballast....... "12 volts not for use with ballast" or "12 volts no ballast required" or simply "12 volts" are typical labels on that coil

The Voltage Regulator (if it used one instead of a cutout relay) and genny are for a 6 volt system so you cant simply add a resistor to fix all that. You can get a 12 volt genny and a 12 volt VR or convert to a 12 volt alternator.

If you change from Pos to Neg ground (like most alternators require) the ammeter leads need swapped or else it will read bass ackwards.

Also if its a coil ignition (NOT a Mag) and you change battery polarity the coil leads also need swapped. Dont let anyone tell you ignition coil polarity dont matter and you can wire it either way, its true you can still get a spark if its wired at the wrong polarity, but the system works best and is more efficient if the coil polarity is corect..

best wishes

John T

I dropped a 12v battery and ballast resistor into my SM and it runs fine, charges good, everything. No longer needs a new battery every year and the last regulator we put on it ran 5 years versus 2 with the 6v battery.

(quoted from post at 15:28:37 08/05/12) I dropped a 12v battery and ballast resistor into my SM and it runs fine, charges good, everything. No longer needs a new battery every year and the last regulator we put on it ran 5 years versus 2 with the 6v battery.

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How does a 6 volt generator putting out about 7.2 volts charge a 12 volt battery?

The resistor you got from NAPA goes in the wire between the ignition switch and the coil. It will only work properly there.

Unfortunately it sounds like you put it in the wrong place, AND it was too little too late. The coil was already damaged from running on 12V for so long.

You need a NEW coil now, too.

Resistors are a funny thing. They DO reduce voltage but not in an easy-to-understand way. You can use a resistor of the correct size on a fixed load like an ignition coil, but on a variable load like an entire tractor, they won't give you a reliable 6V output.