Signal light problems

I think the black wire is horn and on same circuit as dome. Signal switch assemblies are so flimsy that a bad upper column bearing or other misalignment of parts can interrupt them. I can only suggest you loosen the column mounting bolts and wiggles the whole assembly around a bit. There is a little movement left and right plus slotted mounting allows up and down movement. If you find a sweet spot, draw the thing up evenly by the upper 2, leave the lower for last.