I purchased and installed a new Jaguar Nardi steering wheel and adapter hub. After I installed the new hub adapter and steering wheel the horn worked. Then I took it out for a drive and the horn would randomly honk when I turned the wheel or pushed the wheel in or to one side or pulled on the wheel. I did not take pictures or take notes as to how the original steering wheel was installed. The parts I have is the new Nardi steering wheel, cast hub adapter with spline grooves and a wedged tapered wider on the back side, (2) half round tapered rings that I think fit in the smooth groove on the steering column and fit into the wedge in the back side of the Nardi steering wheel adapter, (1) large rubber ring with a smooth washer stuck to one end, (1) large copper ring with a recessed center on one side that looks like there was glue in it and it would fit around the outside of the black rubber ring, (1) nylon locking nut that fits on the end of the splined steering column, (1) thin heavily worn down fender washer, (1) brass rod with a round nylon end the other end and a hexagonal nylon end that screwed onto the end of the splind column behind the nylon locking nut. Attached a pictures of my steering wheel and parts. Does anyone have a drawing showing or written instructions as to which ring and other parts go and the direction the parts are facing?

 

The center rod provides power to the horn. The rod should screw onto the top of the column. Sometimes, the hubs are so thick, that there aren't enough threads for the rod ro screw in. My guess, is that the rod is not screwed in, and is bouncing around, making contact with other metal parts of the column, providing the ground path, setting off the horn.
I soldered a wire to the top of the rod to provide power to the horn button. Ground is provided by the horn button clipping into metal portions of the wheel. If that is not the case, you might have to provide a ground connection.