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Discussion Starter #1
I have always purchased package deals but I got a set of lights and do not have a wiring harness to go with them.

So my question is what wiring would you recommend buying when wanting to run new electrical? I figure I would buy a spool as I know I will come across other projects for the FJ that will need some wiring done here and there and just want to make sure I buy decent wiring that will last and will work.

Any recommendations before I run down to Home Depot and pick up a spool of black and a spool red wiring?
 

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Disclaimer: You'll probably be absolutely fine with something off-the-shelf from Home Depot. Some of my wiring is that. However, if you want to go the extra mile and do rock-solid instead of "just" good enough:

American-made, pure copper, stranded wire. Make sure the insulation is rubber or plastic or silicone, not the eco-friendly plant-based coating that animals will like to eat.


  • "Copper-clad aluminum" wire is lighter weight and less-expensive than pure copper, but doesn't conduct as well.
  • Solid wire conducts better than stranded wire of the same size, but is more susceptible to breaking. In a moving, rumbling off-road vehicle, stay stranded.
What size wire? Blue Sea System's guide is complete but probably overkill for most of us. This chart is the one I usually go to because it's easier for me to quickly read.

In practice, a spool of 12-gauge wire will handle almost every peripheral you might possibly want to add. It'll be thick enough that there's no fire risk but small enough that it's not clunky to work with. Most connectors and soldering that you might need to do can be made to work with it.

If you're going to run "high current" stuff - 30A or more (probably not the case for most light addons), I'd recommend specifically looking to buy welding cable - as these cables are specifically built to carry much more demanding current loads than "normal" (usually this just means they have more copper inside, which means they'll conduct better).

Definitely at least buy equal amounts of wires in two colors - I prefer red (positive) and black (for negative), but some folks are red/white or black/white people.

Finally, consider picking up some "split loom" or "corrugated tubing" that's just big enough to fit whatever wires you'll be running. For this, I'd recommend ordering online and being sure it's explicitly a high-temp/heat-resistant tube. Once you run your wires, add the tubing around them. The wires will be doubly-protected from abrasion and sharp edges. If they pass near hot parts of the engine, they'll have an extra layer of thermal insulation, too.

I actually bought a variety set of wire spools in 10 colors, so that I can color-match what's already in existing harnesses, in addition to using red/black for my own harnesses.
 

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To end up with a clean, reliable and safe harness, there are multiple things you need to do before running out and buying wire ... and you are not likely to find the type of automotive or industrial wire you need at Home Depot.

1. First, you need to determine the conductor size (AWG, or American Wire Gage) you will need. This will be determined by the maximum load current of your lights, and the total length of wiring from your source to the lights. That is the length of BOTH conductors, if you decide to run separate power and ground wires. As noted previously, the Blue Sea wire gauge selection table makes this easy.

2. Second, you need to select the stranding, the number of individual wire strands of a specific size. For a given AWG, there are many different stranding options. The larger the number of smaller gauge strands, the more flexible the wire will be.

3. You need to determine the kind of insulation required. This will be determined if you intend to run the wire in the engine bay, with the high temperatures the insulation will have to withstand for years, or if any of the wiring will be directly exposed to sunlight. Common insulation materials are polyethylene, PVC, PVDF, ECTFE, PTFE, nylon.

(See: https://www.awcwire.com/insulation-materials)

The different insulation materials will have different operating temperature ratings, abrasion resistance, etc. Common operating temperature ratings are 60C, 75C, 90C, 105C, 125C, and 200C. Some silicone materials have even higher temperature ratings, but are very soft and extremely susceptible to cutting and nicking.

4. I use surplus MIL-spec aircraft wire with fluoropolymer insulation (PTFE, PTFE-FEP or ECTFE) rated at 105C or 125C. This typically has a high strand count, and frequently is silver plated for extreme ease in soldering. I run it inside flame-proof silicone-over-fiberglass aircraft sleeving.

One source is Skycraft Surplus in Florida (https://skycraftsurplus.com). Apex Electronics in Sun Valley, CA (https://www.apexsurplus.com/Store_Gallery.html) used to have a very large wire selection, but I haven't been there in a few years.

In any case, route the wiring inside high-temp solid or split convoluted sleeving (or the aircraft sleeving mentioned above), protected by an appropriately-sized fuse or circuit breaker near the B+ source, and of course use a relay to switch the load current, with the in-cab switch carrying only the relay coil current.
 

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Discussion Starter #5
You are all awesome thank you very much for the information and new tools to add to my list of things to use when needing information!

I knew I didnt want to just use off the shelf wiring but I figured that would get at least ones persons attention and that they would hopefully offer up an answer.

This is why I love this forum and am convinced that between it being a Toyota and this forum it will far outlast me.
 
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