Fix a broken car horn by cleaning the connection where the wiring attaches to the horn. The location of the horn exposes this connection to the elements, so it corrodes easily. Clean any corrosion, and reattach the wires. Test the horn to see if it works.
Another common problem with car horns is a blown fuse. Use the owner’s manual, and locate the fuse panel in the vehicle. Consult the diagram on the back of the fuse panel cover, and find the fuse for the horn. Remove it from the panel, and check the wire inside. If the wire is broken, replace the fuse with a similarly sized one. Sometimes fuses blow without any apparent reason, but typically continue to do so until you fix the underlying problem.
Relay switches also cause horn problems. The owner's manual is useful in locating the horn relay. Relays are more expensive than fuses, and you must replace one with the same part number.
If these methods do not fix the horn, take the car to a professional. The horn switch and clock spring, other potential sources of problems, require removal of the airbag assembly for service. Static electricity from dragging clothes across the car seat can cause the airbag to expand with lethal force.