how do i repair horn on 2004 silverado

Did you do anything with the steering column or steering wheel lately ? sounds like your not getting electrical current from the steering wheel switch to activate the horn. The horn relay works because it honks when you use the fob to lock the truck.

Check all fuses connected with the horn. Then the wiring from the fuse box to the bottom of the steering column. If that doesn't proof to be the case. The horn sound is most likely steaming from the alarm system. The sound might be generated by alarm using power from the battery to power the trucks horn, kind of interfacing short-cut used by dealers. Try disabling the alarm system. After disabling the alarm try locking the truck, if no sound is generated, Then your only other option check the horn. This not ease for any 1st timer. If you attempt to proceed my best advise to at least use a good manual one that explaines step-by-step procedure removing and replacing the horn. This is a little more complicated if you also have a tilt steering wheel. This can accomplished by having the needed tools such as a steering wheel puller and snap-ring pliers and also maybe having the truck non-opt for a day or so. GOOD LUCK!

Forget all that crap! It's In the wheel and most likely the horn ring. A relay won't prevent the horn working only in one spot. It works or it doesn't. There is also a part on back of the bag area underneath that can do it also. Pull the steering wheel and clean or replace those contacts! The parts are cheap to replace if you are capable of doing to yourself. Don't remove the airbag u less you know how it could kill you and has happened!

does any one know the relay is located

When you say its the contacts behind the steering wheel would that make it not hav e power at the fuse box