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[jefrs]

PeteF - dunno, on two occasions it stopped the car pulling out into me. I was making avoiding actions at the same time. The one from the right had me nearly up on the pavement.

[Edward]

Jefrs, the output of the alternator has no relevance to the use of a relay when fitting a loud horn. The relay is used to allow a large current to be drawn without damaging the original wiring. The original horn wires are used to trigger the relay contacts and the current is then drawn through an additional heavier duty fused wire. Some horns, such as a Stebel Nautilus draw so much that a relay is vital to avoid damage to the wiring loom.

[Leon Novello]

Autobarn, Supercheap and maybe Repco, sell Arhooga horns in Australia.

[jefrs]

Edward, the wiring used, certainly on the C5, is at least 10A because the smallest fuse is 10A; the wiring must have greater current capability than the fuse or the insulation melts. In other words we're good for 120 watts of ancillaries. The capability of the wire can be determined from its conductor diameter, the wiring used looks like 10A or 15A, they did not skimp on it. So there is no need for another relay for the additional horn.



Some of the models are equipped with two horns to start with, and no additional relay. The wiring system is based around that big 220W alternator, when fitting auxiliaries one should not rely on running stuff off the battery but within the capability of the generator. The C5, and hence Bullet and CGT, can run a pair of spot lamps, the earlier models with the smaller alternator cannot.

[PeteF]

However, Jefrs;
The relay is also there to protect the switch. If you start switching 10a with a switch designed for 5a (say) it's not going to last long.
And as Edward points out, the output of the alternator has no relevance to the need or otherwise of a relay. Unless, of course, you are sounding it continuously.

[jefrs]

PeteF, the switch is capable of powering two horns, on some models it /is/ used with two horns, without a relay. I checked all this and used it with two horns. Some horns, notably cheap ones, do draw more power than others. The Bosch horns I used were pretty efficient and do draw less power than some to produce 93dB at 7 metres (industry standard dBA) aka bloody-loud. They recommended fusing at 16A but I found they actually drew less than 5A together and did not blow the 10A "signalling" fuse with everything turned on (on this circuit, turn flashers and brake lamp). They do want to be fused and the fuse box is up to the job. Those horns appear to be 26W each, 52W paired, indicators are 10W each, brake is 21W, 93W total, plus flasher relay and call it 100W - and the fuse can power 120W, so can the wiring. I checked that, Fluke meter.



The wiring diagram in the handbook is more than iffy. There is a revised diagram on here somewhere, plus I have traced and revised the diagram myself.

[vince]

A good pair of airhorns! its surprising how alert people become when they think your a 40ton truck bearing down.

[jefrs]

PeteF, when designing-in any auxiliary power circuit, even an intermittent one, it is very unwise to rely on the additional power from the battery. Everything has to be taken into consideration, the wiring, fusing, switching and generator output.



Have you've ever ridden a bike with 6V electrics and watched the lights dim out when you applied the horn?

[Paulk]

I'm with PeteF on this one. Whatever the current you can take the horn operating current (via the relay) direct from the battery and will get much less voltage drop and not put any additional strain to the bikes standard wiring and switches.

[PeteF]

I regularly ride with 6v and no, I've not noticed any light dimming when the horn is used.