How to check and fix a car horn that is not working

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  • OVERALL DIFFICULTY INDEX: 2/10
  • IF YOU HAVE NO TOOLS, YOU SPEND $10 TO GET THEM FOR THIS JOB
  • IF YOU HAVE NO EXPERIENCE YOU SPEND 1 HOUR TO CARRY OUT THIS JOB
  • RISK OF INJURY DUE TO AIRBAG - SEE BELOW​
BEFORE YOU START
  • If while following this horn troubleshooting method, you find the need to remove the driver's airbag, then you need to stricly observe the safety precautions described here under. Failure to do so, could falsely trigger the airbag while being handled, which is of an utmost danger. 
  • Injuries resulting from a triggered dismantled airbag can be life threatening.
DISCLAIMER:
Our pictorials are of informative nature and do illustrate works carried out by ourselves at our own premises for our own use and satisfaction.
Readers who envisage to carry out similar works inspired by the below method shall do this at their own risks and liability.

Step 1: start by checking the horn itself

One or two horns are found in any car or van and can be found inside the front bumber.
Access to the horns is usually easy and requires no dismantling of any bumber part or fender mudguard.
This horn is shown in a 2009 Renault Trafic van, to the left side of the vehicle and simply accessible by laying down beneath the front bumper.
Take out the nut that holds the car horn to its fixing plate, disconnect its wire and remove it from the vehicle.
Inspect well the body of the horn and you will notice light white corrosion over its metallic parts. This causes the horn to fail completely or at least to have its noise reduced and deformed.
Clean the metallic part of the horn with a wire brush, then apply a penetrating oil like WD-40 to the electrical connector and the central nut. Do not hesitate to replace the nut by a new one but in all cases, make sure to brush the screw very well as this is the mass connector of the horn.
Try now your horn prior to refitting it to the vehicle and you will notice that it works like new.
Push hard the horn bolt againt the negative terminal of your car battery and use any wire to connect the 12V battery lead to the horn connector to test the horn itself:
If it works, then you need to proceed to step 2 below.
If it doesn't, then you need to replace your horn.

Step 2: check the fuse in the fuse holder inside the car dashboard

Find out where the fuse holder is located inside your dashboard and identify the fuse of the car horn.
Take it out, check it visually for continuity, or use a multimeter to test it.
Refit it or refit a new one of the same rating while making sure it holds well in its place.
Try your horn to see of this fixes the problem or else proceed to step 3 below.

Step 3: check the horn button inside the steering wheel

This step requires the removal of the driver's airbag which should never be carried out without dismantling completelty the car battery.
Nevertheless, the purpose of this tutorial is not to show how to remove the steering wheel panels and the driver's airbag, rather to continue troubleshooting a defective horn.
If you find horn contacts like in this steering wheel of a Renault Trafic van (or Opel Vivaro, Nissan Primastar), then you can easily test them using a multimeter. Select the DC volt, put one lead on the steering wheel central nut and the other on the bare contactor. It should read 0V, then 12V once you push the contacts so they touch each other.
If you find no contacts, especially when the steering wheel contains many buttons for other commands or controls, then you need to check and test the clockspring behind the steering wheel, inside the steering column switch.
Click on the below button for more.

Recap of car horn troubleshooting: probability of failures

The below table lists the most probable horn failures and how to fix them.
Failure
Probability
How to fix
Corroded Horn Body
90%
Brush, clean and apply penetrating oil.
Blown Fuse
1%
Check horn and wiring before replacing fuse with a fuse of the same rating.
Defective steering wheel contacts
1%
Contacts are simple and should run trouble-free for the whole lifetime of the vehicle.
Broken horn and airbag clockspring
8%
Occurs on vehicles with high mileage. Often triggers the airbag light on the dashboard.

See also...