I am converting farmall h tractoer electrial system from 6 volt to 12 volt. Need a diagram of wiring using an alternator

There seems to be plenty of information available online - the wiring is relatively simple and basic, though the 6 volt version with a 4-wire regulator is a little more complex. The 12 volt conversion with a single wire alternator could hardly be simpler.

It seems the ignition is by magneto. Apart from the stop control these units are self contained and if the engine has a good cranking speed and the magneto (and engine) is in good order the engine should start.
The magneto is usually reliable with just the contact breaker points needing periodic attention. When the magneto fails it is a task for a specialist to sort out as a rewind is often needed...

Only thing needed is to change battery , leave wires alone , unless there is a wiring problem , wiring diagrams are avalible on internet, pdf ...

Sounds like your still running power thru the original regulator also. Disconnect the original system completely so that your running power directly from alternator's inboard regulator and to the battery. Nowhere else.

from scratch... well are you using the factory style of alternator or something different as you didn't mention the age and it could be: 12 volt positive or negative ground, or, 6 volt positive or negative ground. Or do you have a starter/generator or ??? Further research suggest you have a generator which would mean you have a voltage regulator somewhere... SO please help us help you. We need to identify your system before we can help... Pictures would be great. Numbers would be good, type of battery would help...

Voltage conversion necessitates the replacement of all 6 volt light bulbs and motors with 12 volt light bulbs and motors (including the starter), plus the addition of a ballast resistor to the ignition primary so that the ignition primary can continue to operate on 6 volts. You will need to refit a 12 volt starter solenoid, alternator, and regulator to the vehicle as well. Needless to point out that you will also need to replace the radio. You can use the original wiring if it is in good condition, and all switches should operate adequately as long as their insulators are still intact. The 12 volt system uses less current than the 6 volt system, so there should be no problem with wire gauge.
IMPORTANT: If the original system is POSITIVE GROUND instead of NEGATIVE GROUND, you will need to verify the polarity of all motors you replace, plus reverse the polarity of the ignition coil primary.

to change the points to electronic you will need to get the manufacturer of the distributor and contact them for a compatible electronic kit to replace the points or replacement distributor
to fit an alternator , get one with an internal voltage regulator ( talk with an auto electrician for the best unit --it is not necessary to go big amperage units so one about 35-60 amps will suffice and cheaper as well)
wiring will be the same as will fuses (neither volt sensitive)
gauges will have to be changed to 12 volt units
bulbs changed from 6 volt to 12 bulbs and switches will be the same as they are no volt sensitive
basically the same circuit can be used and the only place to be careful is the alternator wire to the battery and the charge light or volt gauge ( auto electrician can advise here )
starter motor will have to be changed to 12 volts and you will again have to get the replacement unit from an auto electrician as the bendix pitch , movement and mounting neck will be critical
wisconsin did not make electrical components but used off the shelf companies such as delco remy, lucas , bosch, ac etc for the accessories to the engine
it is an interesting project so collect as much information from auto electricians and web sites to help you

Use this link:

http://www.antiquefarmalltractors.org/forums/index.php

Then Register (upper right corner of page) after that post your question there. These guys are serious Farmall Tractor people they will be more than happy to help you.

TRY THIS.