Negative/Ground wire

philh wrote:
Red,

Please explain the why and how you dipped in acid before soldering

I used what I had handy in the garage, either phosphoric acid or muriatic acid - can't remember which. For soldering, you need the wires clean and shiny otherwise the solder won't work well, if at all. If wires are tarnished or corroded, soldering flux won't help. Like when soldering copper pipes, you need the copper clean and shiny (with emery cloth or wire brush) before soldering. There's a few methods to clean copper wire, one common method being vinegar (acetic acid).

Wires that were in the junction box that didn't have marrettes pointing up and filled with water didn't need to be cleaned with acid and soldered just fine after stripping back insulation a bit. On the tarnished wires, you can strip the insulation back a long way and still find tarnished copper because the moisture wicks inside the insulation jacket.