wire

I was told to get 12/3, 12/4 wire. I thought that was for like extension cords and a/c power or is copper wire just wire for dc and ac both

For what are you using it? You are partially correct that 12/3 and 12/4 (meaning 3-conductor and 4-conductor, 12 gage; respectively) are specs for extension cords, but they can be used for DC wiring with no ill effects. The wire doesn't care what's going thru it, and I use 12/3 rubber jacketed heavy-duty extension cord for more than a few things on my XJs (I also like to use 16/2 or 18/2 for running signals and bypass switches, because that way it's covered twice and I only have to pull it once.)

For DC, I probably wouldn't run anything REALLY heavy on 12 gage, but it's heavier than most of the wiring in your harness (the most-used automotive wiring gage is 16, which just seems really anemic to me...)

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I've had poor luck using rubber-coated zip cord in places where there's a lot of exposure. That might be less important outside of New England, but the rubber doesn't age well, risking shorts, and corrosion will often go deep into the wire where you wouldn't expect it. The strands themselves are usually finer than those in automotive wire, too, so when they do corrode, they just disappear. It's fine for speakers, but I'd still favor plastic coated wire for automotive jobs, and for non-audio stuff, wire with fewer, heavier strands.

I'll agree with you on using zip cord - but that's not what I'm talking about here. I'm referring to the good heavy-duty double-insulated extension cord, which I've used for project wiring all over the country. As long as you do a good job keeping the ends sealed, and route it away from obvious hazzards, it will serve quite well.

Hell, I don't even like zip cord, and I don't use it inside the house, let alone on my vehicles!

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