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Old 22 April 2009, 15:54   #1
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Got the horn but can't do anything about it.

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?
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Old 22 April 2009, 16:39   #2
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Wiring sounds right.
Maybe the horn's knackered, or there could be a short in the wiring?
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Old 22 April 2009, 16:48   #3
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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
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Old 22 April 2009, 16:53   #4
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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
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Old 22 April 2009, 16:54   #5
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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?
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Old 22 April 2009, 17:19   #6
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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.
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Old 22 April 2009, 17:43   #7
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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
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Old 22 April 2009, 18:28   #8
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Thanks Astra and Geoffs. That's been copy and pasted for future ref.
Off to order a new horn as it must be shagged.
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Old 22 April 2009, 22:00   #9
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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.

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Old 22 April 2009, 22:02   #10
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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.)

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