Electrical help is needed

"aberson Bresident of the FullyAssed Committe" (emaxxbl) 08/31/2016 at 19:14 • Filed to: None

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Basically I want the horn on the alfa to only work with the ignition on. The way it is now it works with it off or on. I do have three unused terminals on the ignition switch. How would I go about doing this without hacking the wiring too bad?

The diagram is crazy basic. The battery doesn’t directly go to the fuse panel, it goes through the starter and ignition first.

The diagram is basically saying the fuse for the horn goes straight into the relay which the horn and horn button is directly connected too. AFAIK this is the proper way for it to be hooked up.

lone_liberal > aberson Bresident of the FullyAssed Committe 08/31/2016 at 19:27

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You would find an available fused, switched 12v terminal on your fuse box and run a wire from there to the relay replacing the existing one that is constant 12v.

aberson Bresident of the FullyAssed Committe > lone_liberal 08/31/2016 at 19:39

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That makes sense. Thanks

tpw_rules > lone_liberal 08/31/2016 at 19:40

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Yes, this is what you want. If the horn switch grounds the relay coil, then all you need to do is supply a few hundred milliamps to the positive side of the relay coil from a switched fuse. They make accessory taps which split one fuse into a fuse and wire. If your fuse box is compatible, get one of those, plug it into the fuse for something that doesn’t work with the ignition off, and wire the wire to the relay. If you do it right, the only thing you will change is the relay which is easily replaceable.

I did all this to make the headlights on my car turn off with the ignition off.

dogisbadob > aberson Bresident of the FullyAssed Committe 08/31/2016 at 19:44

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It’s an Alfa. Be glad the horn works at all :p

cbell04 > aberson Bresident of the FullyAssed Committe 08/31/2016 at 19:53

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Careful one of these oppo guys will trick you and you’ll end up with a horn wired to the brake pedal.

Die-Trying > aberson Bresident of the FullyAssed Committe 08/31/2016 at 19:54

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you would need to check the fuse block to find a switched portion of it......... there are usually portions that are always on, and there are sections that are switched(comes in from the junction block,through the switch, and back to the fuse block).........

horns are supposed to be always on........

but find a portion of the fuse block that are switched, and run from there to the relay, from there you could change the set up so that the relay is always powered(switch on), and that the horn button activates only the ground(ground post on relay through the horn to a body ground), OR just keep it regular, where the hot wire from the fuses goes through the horn button to the relay, to the horn.......... that make sense?