Generally, a switch contact will be scratchy but not completely quit working. Usually when the output is ZERO, it's becuase there is no contact to the source. You can probably download a schematic of how the wiring is suppose to be on your guitar and you can open up the guitar and have a peek.... Make sure there are no loose wires and make sure everything is securely soldered. Might just need to resolder the lead going to the switch.