switched 12V problem

ok, now I have a really tough problem. It seems that most of the switched 12V from the underdash fuse box is gone. Where the heck does it comes from, what generates it ?

P.S. All of the connections seem to tight and all of the fuses are good, including under the hood

Ignition key "on" circuit. Check it in a wiring diagram for your vehicle, preferably not a Chilton's manual.

I think the actual "switch" is the key switch itself, I can't see or think of anything else that would do that. I will replace it and see what happens - should fix it though.

Yep, but it could be in the wiring in the circuit, not just the switch itself. Replace the switch though, its' cheap. If that doesn't do it, start tracing wires.