Thanks guys for all the thoughts and suggestions. Worked on this more today and still no joy. I replied to each of you below thinking others afterwards might be helped with the same or similar problem.
I know nothing about 1946; however, the 47-55st horn button lead is a hot lead (the horn body needs to have a good ground)?
Tim—-If I understand, the replies given in other threads to others seeking guidance in the past, correctly the horn button on the ‘46 grounds the circuit when pressed.
I would get a meter and be 100% sure you have a good ground with the negative lead of your meter (run a jumper to the ground strap or good frame connection). Put the hot lead of the meter on your horn terminal and have someone hit the horn. If you have voltage coming to the horn you need to run a ground wire either from the horn connection bolt or the sheet metal next to the horn to a known good ground. I had an issue where I thought my horn had died. I pulled it off the truck and was preparing to drill and separate the shell to get access to the guts and at the last minute decided to bench test it. I put 12v across the horn and it worked great. I then realized over time the sheet metal the horn was mounted to no longer had a good path back to ground. I ran a jumper wire from the frame to the bolt fastening the horn to the body. Horn now works great. If you don't have good voltage at the horn repeat the procedure working backwards. Check output from the relay. Then input to the relay. and keep working back to the horn button and then input to the horn button.
Dgrinnan—-I spent time today checking ground as suggested in your reply. I am uncertain I understand, “I put 12v across the horn....” I ran a separate ground wire from horn bracket to a braided ground cable on the frame/engine today. Still no joy. The horns worked good on the bench before installation. I think will remove them and retest on the bench. The relay appears to test good, if I am doing that correctly. It reads 3 ohms on the 3 (battery) lug to 5 (switch) lug and zero in all other test combinations; 1 to 3 and 1 to 5. I disconnected the wire from the horn button to the switch lug and attached a test wire from the switch lug and touched the braided ground strap when attempting a test and there is zero response, other than hearing the relay click.
46Sparky, Did these horns blow before you installed them? I believe the horn button supplies ground.
SavannahDog—-Yes, the horns worked when previously bench tested. If I understand correctly the horn button does supply the ground.