Yet Another Horn Gremlin!, Horns not working - group wisdom? Options

[StarBear]

Despite all the postings about horn problems, I have a new one for group wisdom:
1.1974 1.8L; dual horns 335HZ and 400HZ.
2.Original owner (no PO issues!); No long-term storage decay issues – has been is semi-regular use.
3.Horns worked, worked intermittently, then stopped working all together.
4.Horns are OK (tested on direct clip to battery); all other electricals OK; trans ground strap looks OK but haven’t yet cleaned. Cleaned 2 headlight and fuse box grounds.
5.When horn wire touches column ring, the relay clicks (swapped out other known working relays just in case), so connection from horn wire to relay confirmed (so didn’t open steering column to clean inner contacts).
6.Cleaned fuses, fuse contacts and backside fuse connectors.
7.Get only 0.15V across horn hot/ground wires; also across horn hot and ground by headlight.
8.Horn works with hot lead from relay socket 87 (with relay in and ignition on) to horn. Shunt across 30 and 87 gets horn blast, even w/o horn wire touching or ignition on (a clue?).
9.At one time during all the effort, briefly got 12V across the horn wires, but horn didn’t sound (momentary 12V, but insufficient current?).

So… seems like the black/yellow power out wire from relay to horn is the issue. Maybe a loose connection in the relay socket (difficult/expensive to change out, but doable)? or bad black/yellow wire to horn has break (how would one ever rewire that, and how to explain intermittent working)? Anything else possible?

I’m open to group wisdom on this one… (IMG:style_emoticons/default/wacko.gif) (IMG:style_emoticons/default/headbang.gif)