The horns on my Sunbeam did not work 
when the car was delivered last spring. With the new wiring harness and horn relay in place, I decided to investigate and repair.
As a first step, I investigated the horn switch on the steering wheel. I was able to make the new horn relay click when I touched a ground wire to the fixed side of the connection on the steering column, indicating that the new wiring harness was correctly installed. After some cleaning of the round copper plates on the steering wheel and horn ring, I was able to make the relay click by pushing on the horn ring. Still no sound from the horns. A test light at the horn confirmed that power was 
going from the relay to the horns. I needed to trouble shoot the horns themselves.
Sunbeam horns have two connectors, one for power and one for ground. They also have an adjustment screw, visible at the seven O’Clock position in the first photo above. Using an ohm meter on the two connectors, I discovered an open circuit in both horns. I needed to disassemble them, and because they were riveted together at the factory, I got out the angle grinder and took off the rivet ends. You can see the grinding marks in the first picture on the outer edge of the horn.
In the second picture, you can see one one side of the horn after I split the case into its two halves. In the center, there are two copper 
colored coils of wire on each side of a metal tang. The metal tang is part of a switch that allows electric current to pass through the coils, which then become electromagnets. The magnets then pull down on on the other side of the horn (not shown) that in turn pushes on the lower reddish tang, which then opens the switch. In a working horn, the switch turns the electric current on and off rapidly, causing the magnets to switch on and off and the horn itself to vibrate. In my horns, electricity did not pass through the horns to start the process. Where had the circuit failed?
The most likely failure was in the switch. 
Connected to each of the tangs is a small contact point where dirt or corrosion can block electricity. I cleaned them with sandpaper and television tuner cleaner (it must have been in the basement for 30 years). This worked, and as you can see from the illuminated test light, current now passes through the switch.
I reassembled the horns, this time using screws to replace the factory rivets. Back in the car, they work perfectly.
Sunbeam 