I did not read about placing a negative cable on the back housing of the alternator where negative is produced. There is an unused bolt bolt back there. I would be running to the engine & battery.
There's no ground cable at the alternator on many vehicles, because the metal brackets holding the alternator
are the ground path. Steel is a crappy conductor...but there's lots of it, and alternator output on average is fairly low, compared to, for example, the starter motor.
You can make connectors from copper pipe and imagination.
...and a hammer, and a drill. Done that.
Factory acceptable voltage drop is 0.400 amps! Higher amps like lift gate or snow plow, it goes up!
VD tests measure voltage, not amperage. You mean 0.400 volts.
Thousands of years ago in Trade School, I was told that 0.5 volts of VD on the starter +, and starter - was acceptable. I was told that 0.25 volts of VD was acceptable for the alternator + and -.
TYPICALLY, you either see nicely under those figures, or you see substantially more. I can't remember a time when I was right at or near those limits.
So, clean it up before complaining. Electrical spray cleaner, scotch-brite, star washers, solder every replaced or existing connection like the woven grounds. If you have a 400 watt soldering gun (SnapOn R450B) I purchase a new 400 watt tip in Dec. 2020 but I didn’t look for the kit. Get solder & acid because it bites thru oxidation.
Acid flux on electrical soldering is a bad idea. The acid eventually
causes the corrosion you're hoping to get rid of.
Acid flux when soldering copper plumbing works pretty good. The corrosion layer tends to be thicker; as is the overall thickness of the tubing. The acid is neutralized long before it can corrode through the tube--unlike thin wires.
My bigass soldering iron is an ancient WEN Model 450. Has three interchangeable tips; low-watt of maybe 75, medium of 250, and the big guy at 450. VERY nice gun, from a time when WEN build some decent equipment.
Called WEN about twenty years ago, looking for a new "big" tip. Discontinued; they had what stock was on-hand and then there'd be no more. I bought multiple tips of the varieties they still had. Went back later to get even more--and they were sold-out. Damned shame, that was a real nice soldering gun. (I still have a few spare tips...I'm set for awhile yet.) As a bonus, the internal windings are huge enough to test ignition pickup coils, so I can do some ignition diagnosis with it, too!
Visit knewkoncepts online as it is primarily a stereo store but good coonectors, wire doesn’t know what is hooked too!
As long as the insulation will withstand the automotive environment. Some insulation gets touchy around winter weather, high under-hood temps, etc.
I'm thinking there's Industry Standards for the fire-resistance of automotive wire that "stereo wire" doesn't have to meet.
Be careful.