My sentra had more than one relay marked for horn. Found that very strange. That must be why! Try swapping relays around. Maybe fuses too but i doubt that if the horn still works. I'm not a mechanic though, just my two cents. Hope it helps
So I get it replaced check to see if the horn works and it does. Viola Got to pull out of the place I just fixed it turn the sterring wheel hear whats sounds like something braking and no more horn. Thankfully the dealer is going to swap it for me as the part has a warranty
that switch is called a clock spring. It conects the horn contact and also the drivers airbag. if you disconnect the steering wheel shaft anf turn the steering wheel more than 3 times around it will break this spring and you will have to replace it as the horn will no longer work.