2 relays for horn honk

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swederacer

Member - Posts: 4

Joined: June 11, 2008

Posted: June 17, 2008 at 10:16 PM / IP Logged

I read this on this site:

Horn

Horn Blow (-) Output

Connect to the wire from the horn switch that shows ground when the switch is pressed. Some vehicles will require the use of a relay to supply (+) 12 V DC to the horn it self. If the horn does not sound when the key is in the off position, you will need to add at least one relay.

But it does not say how to wire it. I have one relay wired up. 87 horn wire 85 to constant 12V+ 86 to horn output (-) 30 ground. Horn does not honk when the key is in the off position. Does anyone know how to add another relay to power the horn when ign is off?

the12volt

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Joined: March 07, 2002

Location: Louisiana, United States

Posted: June 17, 2008 at 10:22 PM / IP Logged

You can use just one relay to supply 12V+ to the horn itself at the horn. No need for two relays. Connect as follows:

85 to horn output (-)

86 to 12V+

87 to 12V+

87a not used

30 to horn (+) at horn

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the12volt

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Posted: June 17, 2008 at 10:42 PM / IP Logged

i am an idiot wrote:

I think he has a negative trigger for the horn. But his horn is only supplied 12 volts when the key is on. He would also have to permanently ground one side of the horn with the above layout.

The factory relay for the horn only has 12V+ when the key is on. The horn should already be grounded and only require 12V+ to sound, whether it's from the factory relay or the relay he adds.

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swederacer

Member - Posts: 4

Joined: June 11, 2008

Posted: June 18, 2008 at 12:30 AM / IP Logged

I will try your wiring out. I wired up the relay for (-) horns and all would be well if my horn could be honked all the time. I think my Focus' horn only worked when the ign was on too. I know it would work because when I am in programming (the key is in the ignition) the horn does honk to confirm settings. But when I arm/disarm only the siren chirps. I set the programming for horn honk not siren but since the horn can't honk the siren is what goes.

howie ll

Pot Metal - Posts: 16,466

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Location: United Kingdom

Posted: June 18, 2008 at 3:01 AM / IP Logged

Focus horn works all the time, should be a live signal from switch, horn grounded so configure relay to output pos.

swederacer

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Joined: June 11, 2008

Posted: June 18, 2008 at 4:04 AM / IP Logged

This is on a Volvo. From what I understand alot of German cars (even though Volvo's Swedish, seems to apply here too) have their horn wired so that the ign has to be on for it to work. I used to have a 2003 Ford Focus Zx3 and the horn was the same where you try to honk and nothing. Then you turn the ign on and then it honks. It came with all kinds of modifications so perhaps someone messed with the wiring? if it's like you say that the horn is live. It was built by that company that's now out of business.... APC.

i am an idiot

Platinum - Posts: 13,673

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Location: Louisiana, United States

Posted: June 18, 2008 at 10:30 AM / IP Logged

the12volt wrote:

i am an idiot wrote:

I think he has a negative trigger for the horn. But his horn is only supplied 12 volts when the key is on. He would also have to permanently ground one side of the horn with the above layout.

The factory relay for the horn only has 12V+ when the key is on. The horn should already be grounded and only require 12V+ to sound, whether it's from the factory relay or the relay he adds.

I realized the mistake I had made. So in order to not look like an idiot, I deleted the post. But it seems as though the forum is like a hard drive, the FBI CAN recover deleted info. Thanks for letting them know that I really am an Idiot.

the12volt

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Posted: June 18, 2008 at 11:16 AM / IP Logged

i am an idiot wrote:

the12volt wrote:

i am an idiot wrote:

I think he has a negative trigger for the horn. But his horn is only supplied 12 volts when the key is on. He would also have to permanently ground one side of the horn with the above layout.

The factory relay for the horn only has 12V+ when the key is on. The horn should already be grounded and only require 12V+ to sound, whether it's from the factory relay or the relay he adds.

LOL.... If I had not quoted you after you deleted your post, then it would be me looking like an idiot for replying to no one. Don't sweat it, everyone makes mistakes.

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howie ll

Pot Metal - Posts: 16,466

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Posted: June 18, 2008 at 11:39 AM / IP Logged

OK let's start again, no more being facetious, every one has 2 terminals, one will be permanently at ground whilst the other will go to 12v+ when horn activated, either with ign on or off. Alarm feed to 85, 12v+ via 15amp fuse to 86and 87, 30 to horn. If one terminal on horn has 12volts, either permanently or via ign whilst the other goes to ground when when horn activated, then a) one terminal permanent, then again alarm to 85, perm to 86, ground to 87 and 30 to horn. If b) horn terminal only goes live with ign, use relay layout as in a), then remove live leads and replace them with direct battery feeds via 15 amp fuse. Thus only one relay required.

swederacer

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Joined: June 11, 2008

Posted: June 18, 2008 at 12:50 PM / IP Logged

the12volt wrote:

You can use just one relay to supply 12V+ to the horn itself at the horn. No need for two relays. Connect as follows:

85 to horn output (-)

86 to 12V+

87 to 12V+

87a not used

30 to horn (+) at horn

Hey. Well we were both half right. When I read yours I thought about it and just this setup won't work either (at least on my car anyway). It's the same as the relay I already had connected, but backwards. With it like this now there's pwr feeding the horn all the time, but no ground. (the only time it gets grounded is via the horn button at the wheel). So I thought about what would work, and tried it out and I got it working! What I did was I used both relays - and + and wired them together with a common horn output (-). Thanks for the advice. It was your suggestion that got me to think of how to do it.

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