Air horn wiring advice...

I'm installing twin Italian air horns from the excellent Rimmer Bros on my 1987 LR90. The air horns come with a relay and the instructions advise a 20-amp fuse with 2.5 sq mm wire from terminal 86 on the relay to the positive terminal on the compressor and 1 sq mm elsewhere on the horn circuit.

But I want the air horns to be on their own completely separate fused circuit with their own 'momentarily ON' switch on the dash rather than using on the existing push button on the Landy steering column stalk - I can choose which horn to employ under different circumstances.(Sheep and tourists for blasting off the road or waking them up in their camper vans at 4am as I sail by. Or gently use the feeble Landy horn for my nice neighbours, to just say hello).

My question is whether the lengths of 2.5mm positive and earth cables I've just got from Amazon, which claim 30 amp capacity, are ok for the entire circuit and secondly, working from the battery all the way to the air horn themselves located behind the radiator grille, what order do I place the components in? (In any event, I'll earth the compressor at the grille). For the positive circuit do I run the red cable from the battery busbar straight to a nearby fuse holder, then immediately to the relay (and earth the relay's terminal 86 in the busbar) and then take the red wire on to the proposed dashboard switch and then on to the positive blade of the compressor (which will be adjacent to the horn trumpets)? Is that the correct physical order of installation? Or I am I being overcomplicated?

I'm sorry to use so many words, but to those still awake, I have a limited knowledge of electrics which is more dangerous than knowing eff all. Advice appreciated!

You are being overcomplicated (slightly).

You need a 2.5sq mm wire from the battery, through a fuse to pin 30 (this in the 'input'.
Then you connect your air horns (+) using the same wire to pin 87 (the switched output).
Using 1sq mm wire connect pin 86 to earth (or 2.5 sq mm, it doesn't matter).

Then you run 1sq mm (or less) wire from pin 85 to your dashboard switch and the otherside of that switch is fed 12V.
You press the switch, 12V arrives at your relay on pin 85, the relay closes and 12V is passed from pin 30 to pin 87 and the horns wake the parish.

As above with the wiring. Campervans parked willi nilly I have a set of old two tone horns on my series 3, sure gets their attention. [ not an on road vehicle.]

Thank you - that is very clear indeed. Expert advice...
Watch out camper vans parked half way over the potholed single-track road - here comes your 118 decibel 4am wake-up call...

Hector the Bad said:

Thank you - that is very clear indeed. Expert advice...
Watch out camper vans parked half way over the potholed single-track road - here comes your 118 decibel 4am wake-up call...

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You mean they actually park on the road partially blocking a single track lane?

Yes lynall - two wheels on the potholed 'tarmac' and two wheels churning up the soft, almost permanently soaking ground along the edge. Plus the damage to the edge of the tarmac by being driven over. We have hundreds of miles of single-track roads with 'passing places' often used as 'parking spaces' where parking is not allowed, but ignored. Last year, a 7.t ton HIAB delivery truck was blocked from continuing down the road and had to reverse 2 miles back to a point where it could be turned around! Campers, and other vehicles like 4x4s etc block heavy farm vehicles which need the entire tarmac width to get through, seven days a week. If an HGV/trailer truck is forced off the hard surface, it can simply sink on one side and the weight can turn it over onto its side. I have seen this a couple of times in the past three years. Not to mention the rubbish they leave behind and the emptying of chemical toilets into our ditches, and worse, which I won't go into here. And sometimes (but rarely) the arrogant, entitled attitude which comes with it. In areas of remote beauty such as this, tourism can be a curse which actually destroys what it has come to experience. And so it goes on...

Since the Covid pandemic camper vans have bred like rabbits and are infesting places like National parks and areas of outstanding natural beauty. They park all over the place often blocking gateways, may be ok to pass in a car but if driving something large it's
Standard of tourist visiting has dropped considerably, Hope they go back to Benidorm for holls.

Being 75% English myself (and 25% Jack Russell), I didn't want to point any fingers. But sadly the inability to travel abroad form the UK during the COVID fear has led to 75% of the problems up here. It made me feel sorry for the poor Greeks, Turks, Italians etc who normally would depend economically on these ghastly people. The usual European tourists who come here are far more civilised, polite, clean and interesting. What's this got to do with wiring my killer air horns?!!! Onwards and upwards!

Hector the Bad said:

Yes lynall - two wheels on the potholed 'tarmac' and two wheels churning up the soft, almost permanently soaking ground along the edge. Plus the damage to the edge of the tarmac by being driven over. We have hundreds of miles of single-track roads with 'passing places' often used as 'parking spaces' where parking is not allowed, but ignored. Last year, a 7.t ton HIAB delivery truck was blocked from continuing down the road and had to reverse 2 miles back to a point where it could be turned around! Campers, and other vehicles like 4x4s etc block heavy farm vehicles which need the entire tarmac width to get through, seven days a week. If an HGV/trailer truck is forced off the hard surface, it can simply sink on one side and the weight can turn it over onto its side. I have seen this a couple of times in the past three years. Not to mention the rubbish they leave behind and the emptying of chemical toilets into our ditches, and worse, which I won't go into here. And sometimes (but rarely) the arrogant, entitled attitude which comes with it. In areas of remote beauty such as this, tourism can be a curse which actually destroys what it has come to experience. And so it goes on...

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problem is we (UK) dont like motorhomes, banned from many carparks, no overnight parking allowed, no facilities to properly dispose of waste and refuse. if you do stay at a campsite (often £350 a week!) you can't go anywhere carparks have height restrictions or 'no campers'

miktdish said:

You are being overcomplicated (slightly).

You need a 2.5sq mm wire from the battery, through a fuse to pin 30 (this in the 'input'.
Then you connect your air horns (+) using the same wire to pin 87 (the switched output).
Using 1sq mm wire connect pin 86 to earth (or 2.5 sq mm, it doesn't matter).

Then you run 1sq mm (or less) wire from pin 85 to your dashboard switch and the otherside of that switch is fed 12V.
You press the switch, 12V arrives at your relay on pin 85, the relay closes and 12V is passed from pin 30 to pin 87 and the horns wake the parish.

View attachment 279163

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What do you mean by “The other side of the switch is fed 12v”

Air horns are rude. Around here we knock on the offender's door and threaten them with a pistol.

Western Slope Rover said:

Air horns are rude. Around here we knock on the offender's door and threaten them with a pistol.

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Do you watch Yellowstone ??

meego said:

Do you watch Yellowstone ??

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Oh yeah. A bit over the top, but a lot of fun. And Merkin as f*ck.

Western Slope Rover said:

Oh yeah. A bit over the top, but a lot of fun. And Merkin as f*ck.

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Is any of it remotely accurate to real life ? I am up to date with all the episodes and have just started the prequel 1883, which is also fantastic.

meego said:

Is any of it remotely accurate to real life ? I am up to date with all the episodes and have just started the prequel 1883, which is also fantastic.

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There are a few bits and pieces of real life in the west. The cowboy stuff is real. They're the people who live around me, so I like that. That said, it's also just a soap opera.

meego said:

What do you mean by “The other side of the switch is fed 12v”

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There are several ways to wire the relay.
1) is to pass 12V through the dash mounted momentary switch to power pin 85 on the relay
2) is to connect pin 30 to pin 85 and then run a wire from pin 86 back to the dash mounted switch and connect the other side of said switch to earth.

#1 is 'simpler' IMO as there are readily available sources of AUX 12V in the cab/dash.
This means the horn will only work when the ignition is on (AUX is live).
#2 will allow the horn to operate at all times.

miktdish said:

There are several ways to wire the relay.
1) is to pass 12V through the dash mounted momentary switch to power pin 85 on the relay
2) is to connect pin 30 to pin 85 and then run a wire from pin 86 back to the dash mounted switch and connect the other side of said switch to earth.

#1 is 'simpler' IMO as there are readily available sources of AUX 12V in the cab/dash.
This means the horn will only work when the ignition is on (AUX is live).
#2 will allow the horn to operate at all times.

Click to expand...

Cheers. I’m not big on electrickery so that’s why I asked. Reading your earlier post confused me as I read it that 12v was already wired from the battery + to a fuse, to pin 30. I have some stuff to wire up soon and just trying to get my head round it.

All your advice here is really interesting and useful - thank you very much everyone!

Alas, here in the UK only the police are allowed side arms, which is really unfair, so the air horns will have to do BUT…..read on, those of you with nothing better to do (like me)….
‘Deadwood’ is the Gold Standard of Westerns. Frontier town rule by totally insane and immoral criminals, violent, cruel and hilariously funny. Ace Brit actor Ian McShane leads as a mendacious, corrupt saloon and brothel owner who has everyone under his thumb. (2,700 uses of the ‘c- word’ in the first season, apparently). On dvd and utter joy.

miktdish said:

There are several ways to wire the relay.
1) is to pass 12V through the dash mounted momentary switch to power pin 85 on the relay
2) is to connect pin 30 to pin 85 and then run a wire from pin 86 back to the dash mounted switch and connect the other side of said switch to earth.

#1 is 'simpler' IMO as there are readily available sources of AUX 12V in the cab/dash.
This means the horn will only work when the ignition is on (AUX is live).
#2 will allow the horn to operate at all times.

Click to expand...

My wiring is weird but useful - the 12v aux plug on the dash is permanently live and independent of the ignition switch as are all the lights, 4x LED spots on the front light bar and the 2x rear LED spots. So the new air horns will be permanently live and operated independently from the little Landy horn.

Hector the Bad said:

Yes lynall - two wheels on the potholed 'tarmac' and two wheels churning up the soft, almost permanently soaking ground along the edge. Plus the damage to the edge of the tarmac by being driven over. We have hundreds of miles of single-track roads with 'passing places' often used as 'parking spaces' where parking is not allowed, but ignored. Last year, a 7.t ton HIAB delivery truck was blocked from continuing down the road and had to reverse 2 miles back to a point where it could be turned around! Campers, and other vehicles like 4x4s etc block heavy farm vehicles which need the entire tarmac width to get through, seven days a week. If an HGV/trailer truck is forced off the hard surface, it can simply sink on one side and the weight can turn it over onto its side. I have seen this a couple of times in the past three years. Not to mention the rubbish they leave behind and the emptying of chemical toilets into our ditches, and worse, which I won't go into here. And sometimes (but rarely) the arrogant, entitled attitude which comes with it. In areas of remote beauty such as this, tourism can be a curse which actually destroys what it has come to experience. And so it goes on...

Click to expand...

That'll teach you to get a bridge with no fees..
Nothing has changed since I travelled through Skye on the school bus in the 1970s... just the numbers of grockles .