A horn is a device that is frequently used when driving. If the horn fails, it will be very inconvenient to drive. Sometimes the horn is trumpet, and the sound is not like a mosquito, it is very husky, even without a sound. What is the cause of this? Let's see how the horn works. When the horn button on the steering wheel or other position is pressed, the current from the battery will flow through the loop to the electromagnetic coil of the horn relay. The electromagnetic coil draws the movable contact switch of the relay to close, and the current will flow to the horn. The current makes the electromagnet inside the loudspeaker work, so that the vibrating membrane vibrate and make the sound. According to the author's experience, in many faults related to loudspeakers, the problem of speakers is often the failure of speakers themselves. In particular, there are some defects in the location of some designed loudspeakers. When it rains, the loudspeakers are easily drenched by rain, resulting in damage to the horns. When the horn does not sound, the common fault location is not more than 3 points, that is, the horn itself, the horn switch contact and the horn harness. When the failure occurs, it can be checked by the following steps. According to the horn switch, if the loudspeaker sometimes rings, sometimes it does not sound, it is mostly the horn contacts internal contact is not good, some are also the problem of the horn itself. It is mostly due to poor contact of the plug, especially the various contact points around the steering wheel. First check the fuse to see if it is blown, then pull off the horn plug, and use multimeter to measure whether there is electricity in the horn switch. If there is no electricity, check the horn harness and the horn relay. If there is electricity, it is the problem of the horn itself. At this time, you can also try to adjust the adjusting nut on the horn to see if it can sound. If it doesn't sound, you need to change the horn.