Got the horn but can't do anything about it.

[JSP]

My horn is blowing fuses everytime I wire it up. I admit to being a numpty with electronics but positive from the horn onto one terminal on the button, positive on the other terminal to it's own fuse on the fuse box. Negative off the horn to the negative on the fuse box.
Were am I going wrong?

[Downhilldai]

Wiring sounds right.
Maybe the horn's knackered, or there could be a short in the wiring?

[JSP]

Originally Posted by Downhilldai

Wiring sounds right.
Maybe the horn's knackered, or there could be a short in the wiring?

That's the only thing I can think of. Wanted to check I had the wiring right first. What amp fuse would you say? Been using a 10amp

[astra]

Originally Posted by JSP

That's the only thing I can think of. Wanted to check I had the wiring right first. What amp fuse would you say? Been using a 10amp

Hello there you should use ohms law to work that out,hope that helps

[JSP]

Originally Posted by astra

Hello there you should use ohms law to work that out,hope that helps

Total Wiring dunce here Astra. Is ohm some kind of God?

[geoffs]

Ohms law

Volts = Amps x Resistance (V=IxR)

His other useful one is

Watts = Amps x Volts (W=IxV)


eg. if you have a 10 watt bulb on a 12 volt circuit it will draw 1.2 Amps and the bulb has a resistance of 10 ohms

10/12=1.2 and 12/1.2=10

So on your horn, if you have a 10 amp fuse the resistance the horn when operating should be 1.2ohms

Provided your wiring can take it, stick a bigger fuse in and see what happens, maybe best not togo above 20 amps though. However, my guess is that your horn is knacked.

[astra]

As my tutor taught me virgins are rare and what are virgins,once you have worked out that its easy well kinda anyway. my electrics are very poor but if you use ohms law then you cant go wrong.volts,amps,resistance and watts,amps,volts confusing? uuuuuuuuuuuuuuuummmmmmmmmmmmm yes

[JSP]

Thanks Astra and Geoffs. That's been copy and pasted for future ref.
Off to order a new horn as it must be shagged.

[jyasaki]

Ground wire to negative on horn. positive on horn to one side of switch, other end of switch to fuse, other end of fuse to 12V.

Make sure the fuse is appropriately rated (should be in the horn literature; max current is what you're looking for.)

Question: If you take 12V and momentarily connect it directly to the horn, does it sound? Or do the wires melt?

If the former, it's likely your wiring is somehow screwy. If the latter, you've got a shorted horn.

jky

[jyasaki]

Originally Posted by geoffs

So on your horn, if you have a 10 amp fuse the resistance the horn when operating should be 1.2ohms

Except that many of the larger horns use an electric motor to run a pump for air. Can't do that trick with a motor (inductive loads don't play nice with ohmmeters.)

jky

[kitten]

Originally Posted by JSP

Total Wiring dunce here Astra. Is ohm some kind of God?

No that's Om

[yoyo]

Also check the current rating on the switch that is being used, if its a compressor type air horn you may require to install it through a relay.

[JSP]

This is just your run of the mill snail shell type. Came with the boat.