Another bee sting - cant get horn to work in GQ Patrol

[PeeBee]

Loom has been out, finishing up the final run of hook ups before VASS engineering. I cannot get the horn to work, have had the steering bits off, all look fine, it activates by completing the earth circuit, but wont work by pushing the horn pad in the steering wheel, but will squeek like a mouse if direct powered. Almost like its starving of power - any ideas - 3 bloody wires, Killing me. I have tried different horns as well, same root cause.

I have the horn body earthed and the power goes thru the horn to earth. All connections by the wiring diagram, have swapped the relay, nuffink!!!!