The horn doesn't sound, is too weak, or makes a sound that isn't a continuous, uniform note. Two-tone air horns, sirens and musical horns are not acceptable on a road car and get recorded here too.
Wording as it commonly appears on an MOT certificate: “Horn not working or not suitable”.
What does it mean?
The horn doesn't sound, is too weak, or makes a sound that isn't a continuous, uniform note. Two-tone air horns, sirens and musical horns are not acceptable on a road car and get recorded here too.
How serious is it?
Usually recorded as: Major. The tester assesses the actual vehicle on the day, so your certificate is what counts.
What normally causes it?
- A corroded horn unit — they live behind the bumper and get everything the road throws at them
- A blown fuse or a failed relay
- A broken clock spring behind the steering wheel, which usually kills the airbag light and steering wheel buttons at the same time
- A corroded earth at the horn bracket
What a mechanic would check
Press it and listen first, then work backwards: fuse, relay, feed at the horn, earth. If the airbag light is on as well I go straight to the clock spring, because that one fault explains both symptoms and there's no point buying a horn.
What might need replacing
- A horn unit
- A fuse or relay
- An earth repair
- A clock spring in the worst case
Can you still drive it?
Safe enough mechanically, but the horn is your only warning to a pedestrian stepping out. It's a Major fail so it has to be fixed before the retest either way.
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This is general guidance from a UK mechanic, not a substitute for a physical inspection. Only the tester who inspected your vehicle can confirm what was recorded and why.