Originally Posted by
Advent
Your soldering iron is too hot. Oxidation happens faster at higher heat and you're burning the flux, preventing it from doing its job. I'm assuming your iron has an adjustable temperature because you said you use it on full. Set your iron for 550˚F to 600˚F (290˚C to 320˚C).
It was on full really as a last resort. I first tried it at the temps you suggested when i noticed something "fishy" with that particular wire. I was hoping to burn off whatever may have been on it with the temps on full solution.