I am looking for a flux to use on automotive wiring. The wiring is stranded copper wire, and sometimes the strands are discolored some or even black. I usually repair the wiring by crimping and soldering bare butt connectors. Then heat shrink with adhesive lining. When the wire is blackened due to moisture creeping into the wire, the RA flux in the Kester 44 is not enough to clean the wires. I am looking for a liquid or paste flux to clean the wires ends with before I crimp and solder them.
Welcome to the forum!
This is a tough one, from what I know, Rosin Activated (RA) is the more acidic option available for rosin based fluxes, it would normally be the stronger of all the flux options. Kester 44 based flux is commonly used to power through tough joints.
The other thing I can think of is cleaning copper would either to use an abrasive or an old trick of cleaning copper first using a solution of Vinegar/Salt/Water solution (or Lemon Juice to substitute for the Vinegar) and then follow up cleaning the copper with a Baking Soda/Water solution.
Here’s an instructables tutorial on this I’ve found handy in the past: