Making a wiring harness for a H question

In giving my beloved H a run threw the shop, I have decided to make a new basic wiring harness. Down the road I plan on doing a full restore at which time I will buy a recreation of a factory harness. Main reason I'm not buying one now is because the tractor is converted to 12 volt. When I restore, I have set in stone it is going back to 6 volt. Anyways my question is simple. Main power wire to the alternator, is 12 gauge heavy enough or should I go larger? I would think 12 is fine, but if 10 is better, I'd rather learn now then the hard way. I'm probably just splitting hairs here. The original wires I find hard to properly gauge as I'm not use to fabric covered wire.

The size of the wire is going to depend on maximum output of the alternator. If you have a 42 amp alternator the 12 gauge wire should be fine. If you have a 65 or 72 amp unit I would go with 10 gauge.

Don't let anyone tell you that you are better off with 12 volts. I have a 6 volt Super M with fire crater pistons and new rings. It starts fine.

Even at 10 below? If 6 volt was so great, more tractors would have it.

Just how did we use the tractors when they were new cause they started even when it ws cold and below zero we didnt have anythng on 12v cause it didnt exist

This is not a 6 volt vs 12 volt discussion.

ACTUALLY.... Dad's '51 M was delivered brand new from the dealer on December 23,1951. And on December 24 it would not start to grind cattle feed! Yes, it was cold that day, about zero, but That was before it got Char-Lynn P/S, M&W live hyd, and 4 inch high compression sleeves/pistons. It was his first tractor converted to 12V well over 35 years ago. He did many others since then.

Stuart, the record in Garden City, KS is 22 below, seldom below 0. A statement from anyone, including me does not apply to everyone. I bought it in NE KS with 6 volts, I will leave it that way. I have a 350 with 12 volts, I will leave it that way. As Gene said 6 volts was used satisfactorily when the tractors were built. In a way 12 volts is like the recommendation of 0 gauge for 6 volts, which allow dirty connections. I get by with 4 gauge, although some of mine are 2 gauge. So 12 volts allows less maintainence. The best thing on my little used tractors are the battery maintainers that I use on all of them,.

I started it as just a comment, but I was afraid it would start something. The initial question was answered, though.

Well as for me i build 100% of all my wiring harnesses myself and yes i make them look factory even color coded correctly . And for a simple Farmall H that has only four wires going out to the engine one 10 ga. is what i use for the hot wire and 14. ga. for the rest and they are installed in the as i call it the slinky loom and i use extra heavy duty non insulated ends and heat shrink over them . Now as to YOUR CHOICE of VOLTAGE hey that is your call. As for me 6 volt NAH ain't no way i would ever go back to that , it took me 10 years with my S/MTA to give in and CHANGE to 12 . ain't looked back yet . Way tomuch hassle tryen to get it to start on 6 volt , did the new battery cables , did the biggest 6 volt that would fit in the battery box tweaked the Reg. to put out better then the wife tricked out the starter so it would spin easier and all the work and all the MONEY SPENT it still did not want to turn over on a decent day let lone on a COLD day , and SHAME ON YOU IF you worked into the night with the lights on because you were three to five amps in the hole on charging the battery and come morning you had best parked her in the barn bridge the night before or you were NOT going to start . On my personal S/MTA i did not go with and alt. i changed the gen over to 12 volts and it will now put five amps to the battery at night with the lights on. AND THE BIGGY HERE IS that it will start the next morning.

In its unrestored state, the tractor is my go to unit for loader work and pulling what needs to be pulled. I'm in the country, but not a farm. For that reason it is staying 12 volts now. At some point when I have a better idea of what fits my needs better, a skidsteer or 40+ HP compact, then the H is being retired from active duty and will get restored. Once restored, it will be a summer show queen. As for winter, I'm not too worried as it will not see much use and if it does, due to my storage arrangements, its home is a shop that is at least 60° at all time. So the biggest risk there is I need room and it sits outside for 6 hours and is stubborn then. I'm willing to run the risk. Worse case, get the bucking bar out and push it in with the skidsteer/compact tractor.

Having one or two tractors of your own is no comparison to working on a whole bunch of customer tractors for years with that dad gum 6 volt system. It just made life so much easier when IH finally went to 12 volts on the later 450 gasoline tractors. Now days you can pick up a good 12 volt battery most any place that sells batteries. To find a good six volt that will fit in a H or M battery box is near impossible. I put in a new six volt in one of my H's last year. Bought it from John Deere. I wanted to keep that particular H original as much as possible. Every time I hit the starter I think, why didn't I just convert it like I did the other H & M. A cable as big as your arm won't help you one solitary bit if the battery cannot deliver the cranking power. Volts times amps equals, goooooo or not in the case of 6 volts. And it didn't have to be tractors if anyone ever remembers the Chevrolet power glide made in 1950. I jump started that darn thing so many times for my in-laws that I was tempted to put an extra battery under the hood. It wasn't when it was cold that bothered, it was when the mother in law or sister in law had it warmed up good and were up town shopping.. Call Jim, could you come up and get the power glide started. My mother in law always said it was a good car. I told her, but you always see it from the drivers seat, I am usually looking at it under the hood or underneath the car. But , she was a great mother in law, chevy, not so much.

I 100% understand the benefits of 12 volts. That's is why it is staying 12 volts as long as its a work horse. When it becomes an over restored unit with goal as being as absoult close to its original form in 1939 when my great grandfather bought it, it will be 6 volts no matter what head aches it brings.

And I fully respect your decision to get it back to where it was when your great
Grandfather had it. My dad bought both of the H's new that I have. Learned to drive on the '45. We always referred to that one as the old H and the '52 as the new one.

the key to good starting 6-volt systems is large gauge battery cables , i use welding cables for mine , 6-volt batterys arent hard to find , mine was a deka battery lasted 10 years always started fine , 6 volt has more amps but less voltage , voltage will make it spin fast but amps is the power behind it , like comparing HP to torque