I just fought this issue on my 85 k10 Suburban last weekend and haven't read the whole thread to see if I"m duplicating advice, but here goes. My dad thought it was the ignition switch mounted to the top of the steering column, but changing it didn't help. The fusible links near the starter checked out fine with a test light, but I wasn't getting power to the dash when I turned the key. Headlights/dome light/horn worked fine.Tracing the wires, I found wire-nut splices (previous owner) where the fusible link should be near the junction block at the top of the firewall. I pulled the bulkhead connector just below the wiper motor and confirmed I had power to the upper left-most red wire going in (I'm assuming horn/lights/etc, now), but the lower left red wire had no power - until my brother jiggled that wire-nut. I took it apart and the wire-nut almost disintegrated. As a stopgap until I can make a good repair, I used a new wire-nut and found I now had power to the lower red wire. Reconnected the bulkhead connector, reconnected plugs into the ignition switch, and fired it up. If you can check the bulkhead connector for power on those two red wires, it should tell you whether the problem is inside the cab or in the engine bay.
Lol
and fried all the fusible links, I lost ALL power to everything in the cab- lights, horn, buzzers, etc.. And when I replaced them, all problems went away..
