Originally Posted by bustedbenz

I can't imagine many combinations of solder and soldering tool in which a >10sec melt time is considered normal. For the usual brand of basement workbench soldering I've seen done and done myself, it melts about as soon as you touch the tip to the material.

My first thought is run out to Radio Shack (or the local equivalent) and pick up a new iron. They're fairly cheap.

Here's my second thought. I have NEVER seen the part you're working on in person. But I'm going to take one of your verbatim statements: "It's the brush that attaches directly to the plastic "plate", inside the the metal sleeve that also holds one end of the copper coil." Are you trying to let the solder "glue" the brush to a plastic part? You sound experienced with this sort of repair, but I am not familiar with any sort of solder (that is not to say it doesn't exist) that bonds to plastic. So if that's actually what's happening then I *think* you're describing a lost cause from the start. If you're soldering metal to metal then my first suspicion would still be a soldering iron that wasn't getting hot enough.