On my switch it was the starter that wasn't ingauging as I recall. I got a new swith at NAPA for like $25 and it cured it.
I took the switch apart and nothing was too obviuos. The terminals could be wiggles a bit(which may not be abnormal) and I belive the contacts were worn thin.
I'm picturing your contact cracked or snapped off(if I'm still understanding your problem as no juice or intermitant juice at coil).
The diagram for the switch is in simpler diagrams like "starting curcuit; lighting curcuit; , etc. In vol. 2 I think. I still use paper books, the computer <img src="/forums/images/graemlins/notooth.gif" alt="" /> stuff is for you young smart guys with newish computers.
I don't have my book with me.

dave h.
'89 Raider V6 5spd;Aisin Hubs;; Gen2 LS: frt. brakes, rear coils;U.C.arms;R.trailing arms;idler arm; rear LSD axle w.disc brakes ;2 battery system for Dog's fan; relocated ECU; custom bumpers;J.Baker receiver;Conferr roofrack; t-bar crank.