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Electrical guides and mods

453 Horn Upgrade

Modification Details

Like all previous smart models, the horn is an embarrassment. A single unit that's far too quiet.
What we need is a pair of tone matched horns (high and low frequency).

Remove the front panel to access the main horn. It's just below the offside headlight...

...hidden just behind the crash bar.

Look down between the wheel arch liner and the crash bar leg. Arrowed below if the main horn connector.

Pull back the blue latch, press it down and then pull the connector free from the horn.

Just leave the original horn in place. The new offside horn won't be installed in this position.

Look over behind the nearside headlight. Here you'll find the alarm horn.
This does NOT make a noise when you press the horn button on the steering wheel. It's the alarm only.

Use a 13mm spanner or socket to remove the nut holding the horn to the car.

Pull the horn back behind the crash structure...

...and bolt it up where ever you can.

These are my horns of choice. Hella Supertones. They are incredibly loud.

Look behind the offside headlight and you'll see a fixed stud. We'll use this but you'll need an M8 nut. (13mm hex).

Attach one of the horns to the metal straps supplied with the horns. Fit the nut and tighten it up.

Repeat on the other side with the other horn.

All fitted, now's the time for wiring. You have 2 options depending on how much you trust the existing relay and wiring.

The Easy Wiring Solution

First you need to buy this adapter, they are cheap and also available from smartmods with much faster delivery.

Go back over to the offside horn connector, plug the adapter in and slide the blue plastic tab in to lock it.

If you believe the specs of the horns and the maximum amperage of the horn relay,
you can connect straight to the existing wiring. So you just need 2 Y-shaped splitter cables.

These splitter cables will come with the adapter when bought from smartmods.

Plug in both horns, turn the ignition on and give the new horns a go to make sure they are functioning correctly.

Refit the front panels and dress the wires so the don't foul or rub on anything.

The Ideal Wiring Solution

First you need to buy this adapter, they are cheap and also available from smartmods with much faster delivery.

Go back over to the offside horn connector, plug the adapter in and slide the blue plastic tab in to lock it.

Connect the adapter spade connectors to relay connector number 85 and 86.
This will then use the existing horn circuit to axctivate the solenoid in the new relay.

You must then create a pair of cables that go from:
battery - to relay pin 30
battery + to relay pin 87

That means you'll power the horn through the relay directly from the battery.

What Horns Are Best?

Hella Rich Tone (115 dB) 2 x 66W
Hella Full Tone (116 dB) 2 x 72W
Hella Sharp Tone (115 dB) 2 x 42W
Hella Super Tone (118 dB) 2 x 66W

I used the Red Hella Super Tone horns as they are the loudest. They use 132 watts at 12 volts, equalling 11 amps total.

The 453 horn relay has recommended upper limit of 25 amps so the relay and wiring should be ok to drive these horns.

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