ShortScale.org

yes,
i have fixed mustang slider switches before, the basic design of them is really rather simple so the chane of it really being "dead" is highly unlikely, most likely over time the inner workings have shifted and the contact points no longer make contact, take to a good tech to have them worked on for sure!

yeah, usually a good cleaning will work wonders. there's probably just grime in the switches keeping them from making contact.