The main heat range switch on our MIG welder always felt a little loose. In September 2015 it finally gave up. The center hub was split in two, the contacts were eroded and burned from lack of good electrical contact. It was a mess. Can’t buy a new one, but one of the good things about equipment made 30 years ago is that it’s rebuildable. TIG brazed all the burned contacts and resurfaced them. Epoxied and pinned the center hub back together, and made a reinforcing sleeve to strengthen where the crack started. Made a new pointer. Reassembled, and it should be as good as new.