You might have a bad relay. It happens. If the first relay worked for 4 years you have every thing in place so look at connections, corrosion and don't forget to look at the horn button pats as well. Are you running 1 horn or 2? The relay has to provide enough current to work both if you have them. With 2 horns see if you can get a relay rated at higher amps. Check one thing at a time and I bet you find it.
