I have a 39 Cad 60S that may be missing something under the horn button that wont allow me to get the horns working. I pop the cap off and there is nothing to ground the center stud to the body. I have found no springs or anything that even would come close to grounding out the center stud to cause the horn relay to pull in. I have continuity between the center stud and the screw out on the column that the connection is made to the relay. The cap has a cup shaped insert that is held in with a spring steel piece with fingers to hold it into place. Whats missing??
First, I assume that if you ground the contact in the center of the steering column, the horn would sound.
One thing you didnt mention, is a conical coil spring that fits onto the contact, and bears against the piece inside the horn button. The large end of the spring contacts shell inside the horn button. That makes the shell inside the button hot, and when the button is pressed, it contacts the metal parts of the steering wheel or the three wings of the horn ring, grounding the relay contact and blowing the horn. Any flexure of the hotn ring will cause one of the wings on it to touch that shell inside the horn button, and ground it.