TL;DR - Almost all of the electrical wiring I've done in the last 7 years has used shitty wire that needs to be replaced.
Coppe Clad Aluminum. Over time, turns to wire powder. Wish someone had told me that earlier.
For the last year or two - since I installed the Diode Dynamics SS5 Pro lights on the bumper - I've been having issues with them flickering. Initially, I thought this was due to the fact that I'd crimped the connectors onto the end of the 12 AWG wire that I'd used to connect my wiring harness to the pigtails on the lights, but even after soldering the connections, I continued to experience issues.
After soldering the first time, it didn't take long for the flickering to crop up again. This time, I thought that perhaps the problem was that the wire had fatigued where the solder joint ended, so I opened everything up again - in the middle of an In-N-Out parking lot if I recall - and crimped on some new connectors.
A few months later, one of the lights was flickering again. By this point, I was running out of length in my wiring harness, so I knew I needed to come up with a permanent solution.
In the same In-N-Out parking lot, I unwrapped the electrical tape to figure out how to fix the harness one last time, and that's when I discovered that the wire had basically disintegrated! A white powder was all that was left of the first several inches of wire.
What the heck was going on?
Wire powder.
I didn't figure out the problem until I got home. Poking around on the internet, I discovered that the wire I'd purchased - thinking I was getting some reasonably priced 12-gauge copper wire - was actually copper clad aluminum (CCA). Of course, it was labeled as such in the description, and I knew it wasn't pure copper when I purchased it, but I figured that aluminum doesn't rust/corrode, and the wire was cheaper than pure copper, so it would work just fine.
This stuff is even sold as "Automotive Primary Wire."
Frankly, I probably knew - conceptually - the difference between pure copper (also called "oxygen free copper" or "OFC" and copper clad aluminum, and surely, I could surmise - if only from the price - that pure copper was better. However, being a newb, I had no reason to believe that CCA was inferior from a durability perspective.
Cross-section of a single strand of copper clad aluminum vs. pure copper wire. Imagine dozens or hundreds of these strands (at a much smaller scale) for stranded automotive wire.
Well, it turns out that CCA wire is notorious for corroding when exposed to water, and certainly the wire at the front of the Tacoma is exposed to rain, snow, and water crossings. While I'd done my best to seal everything up with electrical tape, water - even just humidity from the air - got in and that was the beginning of the end.
The bad news is that I have a lot of this wire in the truck - I've gone through nearly 200 feet of both red (positive) and black (negative) CCA wire for various harnesses - and now I need to replace it all with pure copper.
And that meant I needed to do some research into what wire to get. In the end, I went with the following, which are all listed as either pure or oxygen free copper, and which have numerous reviews vouching for their purity. In general, EWCS, GSPower, and WindyNation provide good Oxygen Free Pure Copper products (though they may also carry other lesser quality CCA products as well that you should stay away from).
- 1/0 gauge welding cable (10 feet red+black) (20 feet red+black)
- 4 gauge welding cable (10 feet red+black) (20 feet red+black)
- 6 gauge welding cable (10 feet red+black) (20 feet red+black)
- 10 gauge (25 feet red+black) (50 feet red+black)
- 12 gauge (25 feet red+black) (100 feet red+black)
- 14 gauge (assorted colors)
- 16 gauge (assorted colors)
- 18 gauge (assorted colors)
It's going to be a lot of work, but worth it for the peace of mind and reliability of my accessories. Pretty sure I'll need to rewire the following:
- The Diode Dynamics SS5 Pro spotlights on the bumper.
- The Diode Dynamics SS3 Pro fog lights in the bumper.
- The headlight harness that powers the Ultimate Headlight Upgrade (higher wattage halogen headlights) I've installed into the headlight housings.
- The internals of my Bussmann relay block, which I previously though I "bulletproofed" by using "beefier 12-gauge wire." Turns out, CCA is not beefier.
- All three of my communication radios (Ham, CB, and GMRS).
- The 12v power box that I installed in the bed of the truck.
Yay? 
The first of many new harnesses(left). Looks a lot like the first (right), but with pure copper wire, should last a lot longer.
Table saw transformer. Now as electrical workshop.
ProWireUSA is where I get all my wiring stuff. Good quality stuff for a good price.
Nice! I've been happy with the pure/oxygen free copper that I've linked above on Amazon, and it has the benefit of free shipping and easy/free returns should I get something I'm not going to use. I also found WireBarn at the suggestion of a buddy, and they've got good stuff, too!
No surprise you got corrosion. Aluminum has an electrochemical potential of -1.67 volts, and copper has +0.34 volts, giving a difference of 2.01 volts. In aerospace materials selection, for long term reliability, any difference of greater than 0.25 volts has to be specially sealed at the joints. Even anodized aluminum and stainless steel gets a sealant. Stay far, far away from that copper clad aluminum wire.
Interesting. I didn't think the corrosion issue was due to the metals difference, but rather due to water. I say this partially because I unknowingly used the CCA wire on several "inside-the-cab" accessories, and all that wire seems just fine; it's really only the stuff that's subjected to the elements that has had a problem.
It's such a bummer really. I think of all the people who are looking for cheap wire on amazon (or wherever), who - like me - have no idea that CCA was a bad thing. Frankly, it even sounds good to me conceptually... I know lots of large-gauge utility wire is aluminum... coat that in copper sounds fantastic. But of course, that's not the case, and the reason all the sellers on amazon do it are so that they can offer cheap (low quality) wire.
It'd just be so nice if the stuff there was more education, so we could all buy the "good stuff" the first time!
The CCA wire in the cab just has not corroded yet. Being drier helps. Yes, most of the of the high tension power lines use aluminum conductors, with a steel core strand for strength. It takes special techniques for terminating the wire since the aluminum will oxidize on the outside and the oxide is non conductive. That is why they burned down houses when they tried using aluminum wire.
lol, probably true! Probably won't in the lifetime of my truck, either, I'd guess, but that doesn't make it good, and I'm certainly not trying to defend it.
I've gotten everything rewired with pure copper now and besides a slightly lighter wallet, I feel much better. Nice to be driving down remote bumpy roads without worrying about the SS5 lights on the bumper flickering on/off, or that excess heat is being generated on the high-amp-draw headlight circuit.
Also threw in some Deutsch DT connectors to the lights rather than the chintzy barrel connectors I'd used the first time, for good measure.