Just a note on what the horn relay does. It switches 12 volts to the horns, it does not switch the ground. The 12 volts comes to the horn relay from the battery via the connection point mounted to the radiator support in front of the battery. Pressing the horn button on the steering wheel supplies ground to the horn relay, the relay is energized and 12 volts is routed to the horns. The horns are grounded where they are mounted to the radiator support.
This is the important part. The ground from the steering wheel is passed through the flexible coupling that ties the steering column to the steering box. If you look at a rag joint you will notice an electrical connection between 2 of the posts that are 90 degrees apart. I had to rebuild my rag joint to get my horns to work due to corrosion at one of the posts. You can use a meter to check resistance between the steering box and the shaft from the column. It should be no more than about 2 ohms.
Bob Murray 66 Malibu
Greenfield, Indiana (Indianapolis)
TC Gold #49