I found all the 2 colored wires I need on the Sherco-auto webpage.
Great news! Were you able to purchase small amounts of each, or what was the minimum available?
Anyone know what gauge wires I should get??
If I had to pick one size for "most" circuits, I'd go with 14 gauge.
Our trucks us a mix of 10g to 18g or maybe even smaller (not sure what the smallest ones are), but unless you want to size each color as original, you can cover all your power needs with 14g.
The downside is that your harness will be larger if you replace some 16 and 18 gauge wires with the larger 14g stuff.
If you want to try to get the proper gauge to match the original, I think some of Steve83's diagrams do indicate that property. Not sure which though, so here's a link to just one main diagram page (he's got many):
https://www.supermotors.net/registry/media/1100970
Hunt around for the numbers, or PM him here on this site.
But there are some circuits I would not mess with the size, and some that I would even up-size slightly. The Yellow power lead to the ignition switch for one looks small and should go up to 14g I would say.
The Black w/orange power feed to the headlight switch could probably be up-sized one as well. I often see that one and the Brown one looking like they had been overheated a few too many times.
The Brown one feeds all the running lights though, so not sure you want to re-do the entire truck yet or not!
Then there is the large Black w/yellow wire that powers pretty much everything. At a minimum you should be using 10ga wire. I'm pretty sure that's what the Ford wire is, but it has a more robust (thicker) outer jacket so it looks larger. But it's not 8ga which is notably larger still. And all the aftermarket harness companies are using 10g too I think.
So stick with 10g on the main charging loop from the battery, fuse box, splices and alternator.
Do NOT under-size this wire. It powers literally everything.
If you are replacing your ammeter with a volt-meter, you can even shorten this wire and no longer worry about it being an entire loop.
You would run a new section from the alternator's BAT output post directly to the battery/starter relay post for the shortest possible run. The shorter a wire is, the more power it can handle without distress.
Also, I purchased the Blue Sea 12 circuit fuse box. It has both a negative and a positive terminal.
The original fuse box only received power from 1 cable, the black/yellow wire from the alternator.. how do you connect the Blue Sea fuse box to power??
Same way. The Black w/yellow wire now feeds only the POSITIVE side of the new fuse box.
The negative is just a common grounding area most likely.
Got a pic and a part number for the exact model you bought?
Should I connect the Black/yellow wire from the alternator to the Blue Sea fuse box Positive terminal and run a ground from the negative terminal to the body?
Or
Should I run two new wires from the battery + and - terminals straight to the + and - terminals on the Blue Sea fuse box?
Either one likely will work as long as you have good grounds to other points to the body from the battery. The "best" practice on some setups is to run a ground to the battery, but since our Broncos need as many grounds as possible just as part of your upgrading, then the body is likely going to be a decent enough ground to use from the BlueSea box.
Up to you at this point. Just make sure you add grounds to certain spots.
The main large ground cable will still go to the engine block. The closer to the starter motor the better, but any point directly to the block (not just the intake manifold or a bracket) is usually sufficient.
Then add another one of 10g (at least) to the body near the battery.
Then add another one also of at least 10ga between the back of the engine and the firewall. This is usually from the back of the intake manifold to the firewall, but can be anywhere of your choosing really. The most common type is a braided strap with ring terminals at both ends. They're available pre-made just about everywhere and I think are rated at approx. 8g to 4g depending on which one you get.
Many of us are also running a ground between the engine block and the frame. This is one of those that is considered a bit of overkill, but is not hurting anything and can be a good thing. Especially on a Bronco!
And besides, overkill is just enough when it comes to battery cable size and the number of grounds you add.
Good luck.
Paul
