Just wanted to tidy up a loose end here.
I traced the wires back and the purple black wire from the horn switch doesn't go directly to a horn as I thought it would but instead to a
transformer of some kind
The transformer also has a yellow cable going into it, which I haven't traced yet, but I'm guessing it is this yellow wire on the
fuse box. The black wire from the transformer connects to the positive of the
air horn , which, presumably, is an after market modification.
Next step is to trace the yellow cable to confirm, confirm connectivity on all three wires ( yellow, black and purple/black ) and if it's still not working, I assume I either have to replace the transformer or, if that's not possible, get a new horn entirely - recommendations welcome.
Perhaps this is all standard fare for the more experienced Morgan owners - I'm still climbing that hill, probably in the climbing over the stile to get on the footpath stage
