The horn is like a bridge connecting a low power circuit and an electromagnet, and it operates a mechanical switch. The switch either opens or closes the circuit that carries a higher power, leading the horn to make sound. When do you press the button and the horn makes sound, it is actually the low power circuit is activated and runs to your car's steering wheel. Horn is so important that you cannot alert people who drive around you with a worn horn, and it is can be dangerous. Here are some symptoms indicating that your horn goes wrong: if you press the horn button and no sound; if you press the horn button but you can only hear a click; if the horn only works sometimes, you are supposed to check your horn relay immediately and see if the replacement is necessary. We are glad to offer you all BMW genuine OEM horn with a discounted price.