Need help, Wiring Quagmire

I recently rescued a Ford 641 from the clutches of a giant oak tree on a fellows farm. He said it had been setting there for about 1 1/2 years. To make a long story short, we drained the tank, put in fresh gas and a good battery and it cranked right up after about 5 spins.
Here is my current problem. The fellow told me it had been converted to 12V and it did have a 12V battery in it. However, it still had the generator on it. The hot wire to the coil was ran around the front of the engine and was spliced in to one of the generator wires. It did crank up and run. Don't know if it was charging or not. Everything else related to the wiring looked to be just like it was originally with the 6V system.
I guess my question is how can I tell if this thing is still wired for a 6 Volt battery or does it sound like a 12 volt battery was thrown in and they called it good? I've been sitting out there in the shop studying the wiring, but the more I look, the more I seem to get confused. I would appreciate any feedback that you guys can give. Thanks

I am not much help at diagnosing wiring problems from afar.
But I am fully aware of the benefits of 12 volt over 6 volt.
If that were my tractor I would strip the harness out of it and make a new one.
Start with a 10 SI alternator and a 12 Volt coil that did not need a resistor.
Then there are about half a dozen wires in the whole darned system that you need to run new.
I like to solder all my connectors and use shrink tubing. And then go to the hardware store and buy a roll of old fashioned friction tape and make a nice clean harness.
When you are done you have an electrical system that you likely wont touch again for years and years.
For a best diagram on how to wire in a 3 wire alternator and some good info on alternators in general follow the link below.
Diagram is about 2/3 of the way down the page.

This site !2v change over wiring alternator and brackets $130.

Hard to say without seeing it, but it is possible that someone put in a 12V generator (looks very similar to the 6V genny), and bolted in place a 12V voltage regulator in place of the original 6V regulator. The original harness would work just fine that way. That is what I have done to mine. I wanted to keep an original look, but go 12V at the same time.

There are many, many discussions about the pros and cons of 12V vs 6V, and 12V generator systems vs 12V alternators, so I won't go into them. I guess it depends how you want to use the tractor would drive what to do. If you're going to work it, you can't beat a 12V alternator and doing what UltraDog said.

I plan to use this tractor primarily for gardening and working food plots on my property. At the moment, I'd just like to get it running good and I'll make improvements (12 volt conversion) as time permits.
They had supposedly put a good battery in it when I went to pick it up and I was able to crank it and drive it up on the trailer. Yesterday, however, the battery went bad and won't take a charge, so I've got to get another. I'd just like to know which battery to get, 6V or 12V. I don't know how to tell a 6V generator from a 12V, so I'm not sure if the generator was ever replaced. Is there a way to identify them other than checking the voltage? I know this tractor is old and lots of changes could have been made to it, but honestly the wiring and everything under the hood looks bone stock, like it has never been touched (other than the hot wire to the coil).

The first thing to do is to get a voltmeter and see if it's charging. That is, does the battery voltage rise after you start the engine? If indeed it's charging, they did a conversion using a 12 volt generator and you're good to go. If not, you'll need to dig deeper by looking at the generator and regulator markings to see if you have a malfunctioning 12 volt charging system, or simply a 12 volt battery in a six volt system. The starter relay (aka solenoid) should have been replaced as well, and the coil should be marked "12V no external resistor required" if there's no resistor in the circuit.

(quoted from post at 01:09:16 05/24/15) I plan to use this tractor primarily for gardening and working food plots on my property. At the moment, I'd just like to get it running good and I'll make improvements (12 volt conversion) as time permits.
They had supposedly put a good battery in it when I went to pick it up and I was able to crank it and drive it up on the trailer. Yesterday, however, the battery went bad and won't take a charge, so I've got to get another. I'd just like to know which battery to get, 6V or 12V. I don't know how to tell a 6V generator from a 12V, so I'm not sure if the generator was ever replaced. Is there a way to identify them other than checking the voltage? I know this tractor is old and lots of changes could have been made to it, but honestly the wiring and everything under the hood looks bone stock, like it has never been touched (other than the hot wire to the coil).

Click to expand...

es, if you can make a good resistance measurement of the field coils or alternately apply a known voltage ( 6 or 12, either OK) and measure the field current draw, then from this we can be pretty certain if generator is 6 or 12 volt.

Amen to the 12 volt, I do like the kits cause I dont have to fab the brackets and the alt comes with the correct width pulley , but I do make my own wiring harness The ones in the kit are not soldered I to use a coil with an internal resister $20 at NAPA
Boss

There was a resistor mounted near the coil, however, it was bypassed and a wire was ran from the dizzy to a wire right in front of the generator. I'll check for charging when I get it going again with another battery.

JMOR I know how to measure resistance using the multi meter, but I'm afraid you went right over my head talking about field coils and such. I want ask you to explain further because as dumb as I am when it comes to electricity, I probably wouldn't understand anyway. I'll look for markings on the generator and I'm going to put a 12 volt battery in it and get it cranked. I'll then measure the voltage at the battery with it running.

(quoted from post at 15:02:04 05/24/15) JMOR I know how to measure resistance using the multi meter, but I'm afraid you went right over my head talking about field coils and such. I want ask you to explain further because as dumb as I am when it comes to electricity, I probably wouldn't understand anyway. I'll look for markings on the generator and I'm going to put a 12 volt battery in it and get it cranked. I'll then measure the voltage at the battery with it running.

Click to expand...

eal simple. Just remove wire from generator Field terminal, then connect Ohmmeter to that Field terminal and to the kther barrel terminal (ground) You have then measured field coil resistance. Expect about 3 Ohms if 6v and twice that, maybe 7 Ohms if 12v

Ok, I think even I can do that. I'll get it checked out tomorrow and post what I find. Thanks.

Ok, just measured the field coil resistance and it is right at 3.6 ohms. I guess that indicates that it is a 6 volt generator. Can't understand why PO left the 6 volt generator in it and just put in a 12V battery and 12V coil with an external resistor that wasn't even hooked up? With that the case, couldn't I just put a 6V battery back in it with a positive ground and change back to the 6V coil and be good to go?

(quoted from post at 15:34:23 05/25/15) Ok, just measured the field coil resistance and it is right at 3.6 ohms. I guess that indicates that it is a 6 volt generator. Can't understand why PO left the 6 volt generator in it and just put in a 12V battery and 12V coil with an external resistor that wasn't even hooked up? With that the case, couldn't I just put a 6V battery back in it with a positive ground and change back to the 6V coil and be good to go?

Click to expand...

es, you could, assuming good generator, good VR, good cables, etc.

It is not uncommon to find tractors with a 12volt battery and a 6 volt generator. Here we call those "shade tree conversions"

Irony know what you have for a generator. I would look at the regulator. It should be marked 6v or 12v.