ford 8N electrical

I hope I can make my query understandable but I have a Ford 8N that needs a new wiring harness it appears. I can follow a diagram and hook it up but can't understand why this wire goes here and the path of the current and which component it goes to first, second etc. and why. I don't want to know just how but why as well. In this case it has been converted to 12v with alternator, neg ground and has what shows as a 12v coil but says use with resistor. Any help would be greatly appreciated. Thank you.

While what I'm suggesting might not apply directly to your 8n, I'd suggest a beginning electrical theory book or online course. Where the wires go and what they do might make more sense once you've got some theory going for you.

Electronics is what I do for a living, I still enjoy it.

wit getting into deep electrical theory, think of a copper wire as a water pipe. water in, it flows, water out.

electrons in, flows, electrons out. It's not a perfect analogy, but it works if you think like plumbing, with 'pressure' as the voltage, and flow in gpm as the current.

circuits need a complete path for current to flow.

one side of the battery is grounded to the chassis. in your case with an alternator, likely the negative is grounded .

then you have the other post of the battery.

think of drawing a line from that other post as it goes thru various circuits.

when starting it's going from one post thru the starter relay switch contacts, thru the starter and to ground ( other bat post ).

same with going to/thru ignition switch then to resistor, then to coil, to distribuitor, to spark plug to ground.

same with going to lamp switch, to lamps to ground.

just a bunch of unrelated and interrelated circuits bundled up in a harness. some share a common wire coming from the battery, etc.. some don't.

ps.. the coil marked 12v with a resistor is telling you the coil is ( likely a 6v coil ) and can be used in a 12v application with a separate serial resistor inline with the coil primary.

again.. this is a really really watered down version of dc electronics 01, but it might help you understand.

For basic automotive/tractor electrical theory, and how ignition, starting, and charging systems work, it's hard to beat the "FOS-20" manual published by John Deere.

A GOOGLE search will turn up copies on Amazon and ebay.

For a preview of the manual, cut and paste this link into your browser, as it will not work as a "direct"/"hot" link.

http://www.cleancomputes.com/Cub/Blue%20Ribbon%20Service%20Manuals/FOS-20%20Chapter%206-Ignition%20Circuits/index.html

For what your asking for you pretty much need something like the Hays Automotive electrical manual 1654. Or maybe even a class in electronics's etc. The why and how of electrical systems can get very deep in theory and the how and why things work like they do. I many cases if you really want to know how and why thing work as they do you need to understand ohms law and many other theories.

In regards to "In this case it has been converted to 12v with alternator, neg ground and has what shows as a 12v coil but says use with resistor"

A coil labeled "12 volts for use with (or requires) an external ballast resistor" MEANS JUST WHAT IT SAYS as in reality its a 6 volt coil, therefore if used on a 12 volt tractor it requires addition of an external series voltage dropping (12 down to 6) ballast resistor so the 6 volt coil sees the voltage it was designed to handle.

If youre at Neg ground and had an external can type coil with + and - accessible leads (NOT so on some tractors) the coil should be wired so its + receives ignition switched voltage while its - wires to the distributor and its points.

John T