The horns in my 69 Firebird don't work.
I've tried everything I know and looked extensively at YouTube to no avail. Apparently there is no fuse for the horn. At least I can't find one. Is that right?
I put 12 volts directly to the horn (both the old one and a new one) being carful to ground the body-Nothing!
What should I try next?
I don't know if I have a switch problem or a relay problem or something else.

Your Thoughts please.

I'm a bit confused. But I do know if you run 12 volts and a ground directly to a working horn, it will sound. I tested mine off the car that way before I installed them.

I did that of course with my original horns and two new ones. None of them sounded even though they had power and ground.

I've loosened old horns before by filling the inside with penetrating oil and letting them sit for a couple days. Sometimes it works, sometimes not. If they won't make any noise they are probably shot.