I have a 97 Mazda 323 and the horn has stopped working. When I press the horn button on the steering wheel I hear a clicking noise but no horn. What should I check?
Locate your horn (commonly in front of the radiator) and verify the electrical leads are connected and in good shape.
While pressing the horn button, check the voltage between the positive lead connected to the horn and ground. It should be around 12v. Note that it is not necessary to have the vehicle running to do this. Also verify that the resistance between the ground lead and ground is low (less than 5 ohms, typically).
Most likely you will find the voltage fine, indicating you need a new horn. If the voltage is not present, or is low, or if the resistance on the ground lead is high, check the wiring to the horn, since the click sound seems to suggest that the button is properly closing the horn relay.
This is how I have resolved this issue on motorcycles, where the horn is generally much more exposed to the elements and prone to failure.