What causes a car horn to stop working?
3 Answers
The reasons for a car horn not working include the following: 1. Poor sealing leading to moisture: The interior of the horn is sealed, and if the sealing is not tight, moisture may enter during car washing or water vapor may be present in the internal space, which can easily cause the contacts to become damp and fail to function properly. 2. Poor contact at the electromagnetic coil terminals: Some horns have aluminum metal rivets crimped to connect the enameled wire terminals of the internal electromagnetic coils, rather than being securely welded. If the insulation paint on the ends of the enameled wire is not properly removed or the rivets are not crimped tightly, it can easily lead to intermittent contact faults, resulting in poor horn performance. This type of fault is due to the quality of the horn and cannot be repaired; only replacement with a new part is possible. 3. Contact erosion: Prolonged pressing of the horn can cause the contacts to erode, creating impedance. This reduces the current flowing through the electromagnetic coil, weakening the electromagnetic force and preventing it from attracting the armature to drive the diaphragm to vibrate normally, resulting in a hoarse sound or even no sound at all. However, when the horn is pressed repeatedly, a momentary strong current passing through the impedance can still allow it to work normally, leading to intermittent functionality.
When I first started learning to drive, I also encountered a non-working horn and ended up frantically slapping the steering wheel. Later, through trial and error, I found out that the most common issue is a broken clock spring under the steering wheel—that's the coil connecting the steering wheel buttons, which tends to break after too much rotation. Another simple reason could be the horn itself failing, especially for cars often parked under trees, where insects might nest in the horn opening and block the sound. When checking, have someone press the horn while you feel the horn body for vibrations—if it vibrates, the issue is likely with the wiring or fuse. Last time my car's horn suddenly became muffled, it was due to oxidation on the horn's ground wire; cleaning the contact points fixed it. If replacing the horn yourself, make sure to match the model—don’t buy one with mismatched voltage, as modifying the wiring could fry the ECU. Of course, a non-working horn should be fixed as soon as possible—it can be critical in emergencies.
In our line of work, troubleshooting a non-functional car horn follows a fixed procedure. First, use a diagnostic tool to retrieve fault codes and rule out issues with the airbag control unit. Focus on three key areas: the steering wheel button contacts, which often accumulate dust and cause sticking—spraying precision electrical cleaner resolves 70% of these cases; the horn relay in the engine bay accounts for 30% of failures, especially in water-damaged vehicles; and checking the main power supply fuse with a multimeter, as a blown 15A fuse is the most common culprit. Interestingly, in winter, some horns fail due to frozen diaphragms in low temperatures. Modified steering wheels require special attention—poorly connected or faulty clock spring wiring can take two hours to reinstall. The horn, located behind the front bumper, is prone to water ingress and short circuits after wading.
