EXPERT IN AUTO PARTS
17 September 2025 (updated) Table of Contents
You may have seen this happen: the driver in front of you doesn't notice that the traffic lights have turned green; the student driver stops the car for the umpteenth time; someone else leaves the roundabout without signalling. While you shouldn’t use your horn every time you get road rage, your car horn could save you from a serious collision in some situations.
Knowing exactly when to use it is key for any driver. You’ll also need to know the classic causes of horn failure if you want to get it fixed in time for your MOT, as well as how much a replacement costs. We’ll explore this and more below.
Modern car horns are typically electromagnetic devices mounted behind the front bumper or the radiator grille. When you press the horn button on the steering wheel, it completes an electric circuit, sending current through a coil. This energises an electromagnet, which moves a diaphragm back and forth rapidly, producing the familiar honking sound.
Most cars use dual-tone horns (high and low frequencies) for a louder, more noticeable sound. Premium brands like HELLA horns are often installed for their reliability and volume.
Before assuming the horn itself has failed, consider these common culprits:
Quick tip: locate the horn fuse using your car’s manual, and test it before booking a mechanic. It might save you £50–£100 in labour.
If you're handy with basic tools, you can replace a car horn yourself. According to AUTODOC experts, a standard electric horn typically costs between £15 and £40, while a premium one (e.g. a customised car air horn ) can cost more. Factor in about 30–60 minutes for the installation, depending on your vehicle’s design.
Sold by AUTODOC Sold by AUTODOC Sold by AUTODOC Sold by AUTODOC Sold by AUTODOC
-50%
Article number: 3AM 922 000-971
compared to
RRP
£21.23
£10.49price incl. 20% VAT, excl. delivery costs
BOSCH Horn
12V, 110 dB(A), Electric-pneumatic, 60W, Holder may need adaptation
Article number: 0 986 AH0 501
£11.49price incl. 20% VAT, excl. delivery costs
-33%
HELLA Air Horn
Article number: 3AL 002 952-871
compared to
RRP
£18.83
£12.49price incl. 20% VAT, excl. delivery costs
Article number: 3AL 922 000-961
£11.49price incl. 20% VAT, excl. delivery costs
BOSCH Air Horn
Article number: 0 986 AH0 731
£9.99price incl. 20% VAT, excl. delivery costs
Tools you’ll need:
A garage or auto technician will typically charge the following:
Prices may vary based on the region or city. For example, London garages usually charge more than those in the Midlands or the North.
Yes, but only under certain conditions. According to the Highway Code Rule 112, drivers may use their horn solely:
Not permitted:
Misuse can lead to a fixed penalty notice or even points on your licence if it causes a disturbance.
| Situation | Is it legal? |
|---|---|
| Warning a pedestrian of danger | ✅ Yes |
| Beeping in traffic | ❌ No |
| Sounding horn at 12am in the city | ❌ No |
| Alerting when overtaking | ✅ Yes |
Signs it’s time for a replacement or upgrade include:
MOT tip: A non-functioning horn is an automatic MOT failure. Ensure it’s working before your test date.
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Article number: 0524731
£124.49price incl. 20% VAT, excl. delivery costs
-69%
VEMO Air Horn
Article number: V10-77-0911
compared to
RRP
£50.57
£15.49price incl. 20% VAT, excl. delivery costs
-34%
Article number: 3AL 002 952-811
compared to
RRP
£18.17
£11.99price incl. 20% VAT, excl. delivery costs
-72%
TOPRAN Air Horn
with fastening material
Article number: 111 072
compared to
RRP
£27.88
£7.59price incl. 20% VAT, excl. delivery costs
If you're fitting a high-powered device or air horn, you may need to install an inline relay or additional wiring.
Even a small amount of rust or poor connection can silence your horn unexpectedly.
A: Not exactly. It must meet UK noise and safety regulations and be of a sound level that doesn't cause alarm. Overly loud aftermarket horns may not pass the MOT.
A: If you drive in high-traffic areas or on rural roads with wildlife, a louder dual-tone or air horn may offer improved safety and peace of mind. Just check whether it meets UK standards first.
A: Yes. A non-functioning or excessively quiet horn will result in an MOT failure. The horn must produce a uniform sound loud enough to be heard by other road users. It must also be operable from the driver’s seat. Testing your car horn before the MOT can help avoid a failed inspection and unnecessary delays.
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