You know, that's pretty strange! I have a '76 Midget with a brown
wire that has been cut where it exits out of the wiring harness right at
the top fuse in my fuse box. It's just hanging there. I also have the 4
brown wires connected in the white "plastic-thingy". Everything seems to
work on my car (electrically speaking), except my hazard and turn signal
flashers which is due to either or both of my flasher units needing
replacement. But I would like to know what this brown wire is also. And
like yourself the wiring schematic I used was of no help either.