The horn system on a standard car utilizes a relay under the dash of the vehicle, along with a switch and siren. When the switch is pressed, power flows through the relay and makes the horn work. If any one of these components is damaged, the horn will fail. Use the following steps to help diagnose a horn problem.
The horn fuse is found inside the engine compartment fuse box.
Use a test light to see if the fuse has power, and replace if necessary.
Use a test light to probe the horn circuit.
Replace the damaged wire, siren, relay or switch if necessary.