The switch itself is pretty simple. IF your troubleshooting is right and the switch is truly open all the time, either:
1. The contacts are so dirty/pitted that they're not making electrical contact or aren't physically touching. Clean them with a switch cleaner or other tool - gently bend one of the leafs closer (from the base) if they're not touching.
2. One or both contacts are separated from the leaf blades. You have to either press the contacts tighter into the leaf or solder them.
3. You have a break in your wiring, either at the switch lugs, or elsewhere. A multimeter might help you determine this.
Get a schematic though - troubleshooting is tough without one.