How do i wire up a 12v horn?

Hi i need to wire a horn upto my WR400 but im not sure how to do it.

I know i obviously need a horn and a button to press it but thats about it!

Can anyone tell me how to do it?


Well the problem you will run into is that the WR400 supplies 12 volts AC and most horns do not work well on AC. There are more elegant methods but the quick and dirty solution is to use a small 9 volt battery to supply the horn.

Thanks for the reply

So will a 9v battery power a 12v horn?

To be honest im wanting to literally know how to wire a horn up

At a guess i would think a 2 prong switch would go to a 2 prong horn and then add two wires from the ignition coil? (positive and negative)

Does that sound right?


First though I haven't personally done it I'm told a 9v battery will run a 12 volt horn but at a reduced output I suspect. Maybe someone with direct experience can chime in. As for hardwiring it to the bike electrical system it depends on what you use for a switch. If it's a kill type switch where one side is tied to ground you will want to run a wire from the bikes electrical system (this should be the yellow wire that runs to the headlight) to one of the connectors on the horn. I don't think it matters which one. The other terminal on the horn should be connected to the switch. When you press the switch you will be completing the circuit to ground. Again in my experience DC horns don't work well with AC so I don't expect reliable output if you decide to go that route. You'll probably get some noise but it will vary or be non-existent depending on the engine rpm.


I think id be using a kill switch i can get one at my local bike shop.

So it should have two pins with one of them being for a ground wire?

The other pin goes to the horn and then yellow wire from the bike to the horn?

Sorry just trying to make sense,it may well be easier to just use a battery

Yes. That should work.

Cheers :thumbsup:

Both wires on the kill switch will be to ground. One wire grounds to the chasis and the other wire will go to the ground on the horn.If you use a battery then attach to the battery ground and the other wire to the horn. Push the kill switch and you have closed a circuit. Run power from the hot side of your head light switch or battery directly to the horn with a fuse in line if you choose. There are horns that will run on AC or DC. Running power through the switch will shorten it's life span so it's better to use it for the ground circuit.

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