The trick to cleaning the little silvered contacts on such switches is "smooth". Most people want to clean these with an emery board, file, sandpaper, heaven knows what. The problem is that the deeper the scratches, the worse they get. Deep scores are a haven for sparking, which leaves carbon deposits...less contact, more sparking, deeper scores...and on it goes.

Take the switch apart carefully, noting how it comes apart. Burnish the contacts by polishing them with a piece of velum cardstock like that used for soft business cards. Not the shiny ones. Nothing more abrasive than this. You'll find that with just a dozen passes you have a beautifully shinny contact that works well. Unless of course the contact has been burned way down. In that case, yes, sand it smooth and round with 400 grit or finer, then polish with the cardstock. If you had to take off a lot of material, you may have to bend the little metal "see-way" contact you removed during disassembly to assure it contacts the fixed point. Of course you need to polish the see-saw's contacts also.

Me sure the switch is lubed and reassemble. I've had 240's where not a single switch worked, but did not have to actually replace a single one. Just clean and polish.

Good luck!

DS