I have a 1978 K10 Chevy 1/2 ton, 4 speed. It wouldn't turn over, I tried my battery boost, but no luck, so I caught it in gear, all of the lights worked...thought it was the solinoid. Disconnected battery, removed started...noticed one lead was not connected, looked like wire is black, could this be a ground wire for the left hand terminal on starter? Took to the parts store, tested it, was good. Re installed starter, no lights, radio, nothing. Put jumper wire on bolt set up on fire wall (junction block?). Fan and lights worked. Reconnected starter, with red wire, engine cranked (without key being turned). This red wire that I connected to the right side of solinoid...shows continuity at redwire on back of alternator and on junction block?, There are 3 wires coming down to the starter, the 2 already mentioned and 1 that runs down frame rail. Looks like 3 or 4 wires on the right side of juntion block, and none on the left side. One has a fusible link and that one is the only one I have found. I tried to find continuity with the black wire that was not connected and had no luck finding where it goes. Any help would be greatly appreciated!