I have a 99 Chevy S-10 with 94,000 miles. The horn stops working and I will check the 15 amp fuse in the engine compartment fuse and relay center. The fuse will be good and if I change the horn relay out the horn will come back to life for at least the one testing of the horn. When testing it later, once again the horn no longer works, the fuse is good but the relay is now kaput, what gives ?