I have worked on the horn contact several times, as this related to the turn signal switch. When I replaced the original Sunbeam turn signal with one from a Triumph TR6, I needed to make a new contact device.
In short, the turn signal switch is used
to hold a spring loaded electrical contact onto the steering column. A wire leads from this contact to the horn (via a relay). The contact touches a copper ring on the back side of the steering wheel, and the copper ring is connected to the horn button. Why so complicated? The horn button on the steering wheel needs to turn while the wiring to the horn itself is fixed to the car.
My first attempt used a simple copper strip attached to the steering column (green arrow) to contact the copper ring on the back of the steering wheel (red arrow). In hindsight, I should have stayed with this method. I abandoned it because I could
not keep the copper firmly attached to the steering column.
For my next attempt, I replaced the copper strip with a piece of steel that I slipped into a pen top green arrow). The pen top was plastic and therefore insulated the steel contact from the steering column. I attached the pen cap to a strip of metal using epoxy and dental floss. The dental floss gives structure to the joint by increasing the surface area. This approach worked, but because the steel contact fit loosely in the pen cap, it would get stuck from
time to time. The horn would then sound on its own.
My current refinement uses the same pen and contact approach. This time I started fresh with a new (red) pen cap and metal holder to make the installation a bit more tidy. I used the same contact and spring inside the pen.
There are two innovations in this attempt. First, I reduced the play in the contact by wrapping the rod section of that fits inside the pen cap with heat shrink material to make it thicker. Second, I moved the entire setup to the bottom of the steering column to facilitate adjustment. So far, it seems to work well.
Sunbeam 