you hit it with a file and call it good. ifs its all black and not making contact shining it up is a lot cheaper and faster than replacing. yours may be broken and i may be wasting your time but they are pretty thick and should be serviceable. my first model a work i did was taking off the starter to rebuild it because it did nothing. the starter button contacts were completely black. put it in a towel in a vise and some light filing and sanding till they looked new. put it back together and have not touched that starter again.