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The horn on the smart has never been much good and the fortwo 451 is no exception. There are many different kits available which will plug in directly to the standard wiring but be careful not to overload the circuit. The horn circuit is protected by a 20A fuse but it is unlikely that you will get anywhere near this unless you install air horns which will require a different configuration. In this guide we are installing a two piece 'snail' style diaphragm horn.

To start, you will need to remove the front panels. The horn is located to the right of the radiator:

To remove the horn from the car, use an E8 socket (a 10mm hex socket will also work).

Remove the wiring from the back of horn. Pull the black section and the spade connector will unclip. You can now remove the horn from the car.

To reuse the existing bracket, you will need a 13mm socket to separate the horn from the bracket.

If you are fitting two horns, you will need to split the existing wiring. Rather than cutting into the car wiring loom, we chose to build two cable splitters. You will need blue spade connectors, a crimp tool and at least 2.5mm² wire.

Fit the new horns in the same place back to back on their respective mounting brackets. In order to get them to fit, they had to be offset slightly.

Plug the new splitters into the main wiring loom and connect both horns.

Test the operation of both horns with the ignition on before you refit the front of the car. You will now see that other cars take you more seriously when required!

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