What are the functions of the horn circuit and horn relay?


Horn is a sound creating the device. Electrical horns are used in all the automobile vehicles. When the horn is operated, it creates loud vibrating sound indicating that vehicle is coming so that the passengers or the other slow-moving vehicles may clear off the path to passing it. Horn is also used as a calling well to call the persons when the vehicle is ready to start. Lights, breaks, and horns are devices that prevent the accident. Light flashes the road, horn makes the road clear and breaks stop the vehicle, all the three devices make the driving safe from accident. It also contains the horn relay.



The figure shows a diagram of the horn circuit. It consists of an armature, a diaphragm, a winding and a pair of contact points connected in series. When the horn button is pushed, it connects the horn winding to the battery.


The current passing through the winding produces the magnetic field which pulls the armature down, creating a loud click. The armature is attached to a diaphragm. The movement of the diaphragm opens the contact points, due to which the circuit is broken. The cycle is repeated rapidly. The rapid movement of the diaphragm produces a distinctive noise. The tone pitch of the horn depends upon the size and shape of the diaphragm and also upon the path through which the sound must travel.

horn circuit, horn relay


A relay is also used in some systems to avoid carrying the heavy current required by the horn through the steering column and back. The relay closes its contact points to connect the horn to the battery. This way, the voltage drop in the wiring from the battery to the horn is eliminated and higher voltage is available for operating the horn with better performance.

horn relay
horn relay

The horn relay serves a second purpose also in some cars. It gives a warning that the ignition key has been left in the ignition switch when the car door is opened. When the ignition key is in the ignition switch, a special set of contacts are closed. Now, if the car is opened, the door switch will complete the circuit t through the buzzer (upper) contacts and winding of the relay to the battery.

The current flowing through the winding produces a magnetic field which pulls the armature down. This opens the contacts and the winding loses its magnetism so that the spring closes the contact again. The cycle is rapidly repeated so that the relay emits a buzzing sound to warn the driver that he has forgotten the ignition key in the ignition switch. This prevents the car from being stolen by thefts.

Watch the video for practical experience with the wiring of a horn relay.

Also, Read These Posts

  1. What is Headlights Aiming, headlight adjustment or Alignment?
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Creative Blogger And Automobile Engineer.

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