Wiring up an air horn

[wildpudding]

Hi everyone,

Have a Fiamm double air horn set from Repco, having some difficulty wiring it up. Basically can't get it to work, which i'm pretty sure is a fault of the set-up as opposed to the unit itself!

Question, I couldn't trace the wires from the old horn right back to the switch itself, is it ok to just connect off where they would have previously connected to the old horn?

And also, there are 2 wiring diagrams, 1 positive activated and one ground activated, which is the right one to use for my bike?(gsxr250)

Cheers,

Stefan

[megarich]

probably best to use a relay given that the current draw from the compressor to run the air horns will be alot more than standard horns.

Most vehicles are negative earthed.

I'll draw up a pic for you if it will help

[Ixion]

I think the question is whether the handlebar switch is in the live line or the earth - ie when you press the switch does it complete the earth connection , or does it connect the battery supply to the horn. Some bikes are one , some the other.

[ldnz]

Nothing that a $20 multimeter couldn't sort out...

Continuity mode, one line on horn lead (each in turn if your really not sure which is which etc) and the other to chassis or neg battery terminal. Then hit horn switch...

Should be straight forward to bodge the relay straight onto the end of the old horn wires, and run new wires straight from the battery.

That said, I haven't caused a fire on my KR yet with the compressor straight onto existing horn wiring and I use the damn things so much that i've physically snapped two horn switches!

[What?]

Nothing that a $20 multimeter couldn't sort out...

Or a test light - with the key on, test the two wires to see if there is power on either. If Yes, the button earths the horn, if No, then the button delivers the power.
If the compressor doesn't work connected one way, try it the other. If still no go, you will definitely need to wire a relay in. (the original horn was working, wasn't it??)

[Cajun]

i have used air horns on 2 of my bikes. i just use the standard horn wiring, seams fine for the job.

[What?]

Yeah, shouldn't be a problem if the bike has a good electrical system. The short bursts that a horn gets are not going to melt wiring. What might happen is that the switch will weld itself closed, but even that is not overly likely.
The reason I suggested a relay is that the standard wiring may offer too much resistance to deliver full voltage to the compressor, thence less, or no noise produced. It all depends on what gauge wire is used in the loom (with some bikes, usually smaller and Jap domestic models, the wiring is only just adequate for standard current draw)

[davereid]

OK, a standard automotive relay has 5 terminals, I can't remember the numbers but they usually printed on the back of the relay.

The terminals are

COIL 1
COIL 2
COMMON
NORMALLY CLOSED
NORMALLY OPEN

The COMMON terminal is conncted to the NORMALLY CLOSED contact. When you put 12v across the COIL this changes, and the COMMON contact is disconnected from NORMALLY CLOSED and connted to NORMALLY OPEN.

1. Put the EXISITING horn wires onto the COIL of the relay - they will plug straight in. It does not matter which way around you go.

After doing this step, when you push the horn button you will hear the relay click.

2. Run a RED wire, with a fuse from the POS terminal of your battery to the relay COMMON.

3. Run a RED wire from the relay NORMALLY OPEN to the POS input to the Air Horn.

4. Run a BLACK wire from the Airhorn NEG to a convenient Earth.

Tips - Use good quality connectors and crimp them carefully. Place the fuse as close to the battery POS it you can.

Now you can scare the bejesus out of dorks who dont give way, and not melt your wiring.

[davereid]

coil = 85,86
common = 30
normally open = 87

[wildpudding]

Cheers everyone for the advice, managed to get it wired up today, and for those wondering....these things are bloody loud! Heaps better than the 'dying sheep' noises made by the stock horn for that matter.

Though riding today I managed to blow the main 20A fuse for no apparent reason, not sure if its related to the horn or not, but rode home ok with a new fuse installed.Hmmm.

Cheers<

Stefan

[davereid]

Hi Stefan
Your Air Horns will draw more than 25 amps. If they are wired through the main fuse, you will pop it regularly. Best is to use an aftermarket fuse, as near to the battery POS terminal as you can get it. Yeah, I have a set of Hella horns on my 6F - chickens scatter, children cry, old ladies faint, a great improvement on factory !

[Toaster]

Its such a shame bikes come with the most gay wet weak sounding horn. Gimmie one of them diesel train horns....

[wildpudding]

The air horns worked great...for one ride. Had them tied under the rear seat with cable ties, which evidently were not strong enough. The 2 horns have disappeared, so anyone out there with some plastic horns I could buy? The compresser by itself isn't much of a horn...

Stefan

[ldnz]

Bugger! Supercheap auto always has them pretty cheap. At least you won't have to go through the whole wiring drama again.