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Gentlemen ... apologies ... and Ladies,

My original twin air horns on the car have now given up the ghost (after 24 years) and are in need of replacement.

I have purchased a set of triple horns ... for my to give me for my birthday!!! So will not be fitting them until the weather improves (I have no garage) 😪

The wiring diagram below came with the horns, before I get anywhere near trying to fit them and wire them up, I am seeking your advice.

I have pencilled a few questions on the wiring diagram as I am uncertain as to exactly what is what. Could anyone please give me a better indication as to how best to wire them up before I am allowed anywhere near the 'present'?

Many thanks ... and please, please let covid bugger off in order that we can once again grace the roads of the UK with our wonderful cars.



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What is this meant to be ............... The stearing wheel. not a fuse.

I would expect to wire a fuse between the battery positive and the relay pin 30. I am not sure what the power of the compressor is but 15A or 30A would be my guess.

The old horn normally uses its mechanical mounting to be its earth (-ve) connection.

I am guessing that the stared switch is to disable the air horns.

I hope that this helps.

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Hi Alan,

As Ian says - what I think they are showing you how to modify an existing horn circuit, using the top switch to give the option of original horn or air horns and the other switch to disable the air horns.

If you already have (or had) a working air horn set up on your car I would think you could simply replace your old compressor & horns with the new one.  You should then only need to take the wires that went to the old compressor and connect them to your new one.

Good luck,  Steve

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Now that I see the steering wheel as a steering wheel ... Doh! ... it makes a lot more sense - thanks Ian

Back in the day .... a long, long time ago ... I had triple tone horns on my series I Land Rover which I could switch between a single (combined) note or 'musical' tone - I wondered whether the switch shown on the compressor might facilitate this option?

Does anyone have triple tone horns that allow this choice (legal or illegal sound) ...

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5 hours ago, alanh65 said:

I have purchased a set of triple horns.

I purchased a set of triple horns some 50+years ago.

The best way to explan the wiring is that the compressor has a feed terminal top and bottom.

If you wish to just have all horns to sound together then supply the bottom feed of the compressor from the relay pin 87

If you wish to have open sound of the horns then install the link switch at the dash board between bottom and top terminals on the compressor, this will give spaced sound when closed. ( This could be against the Law ) to have spaced sound horns.

The relay is feed at pin 30 from battery poss. via fuse. 30 Amp

85 or 86 to earth the other side to horn push.

The compressor needs a good earth.

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Thank you Martin. It was actually late 60s when I had my landy ... so same sort of time!

Your description sounds like the wiring diagram in my post.

When I am given my birthday present ... I'll wire it up on the bench prior to fitting into hoodie.

Many thanks.

The horns will naturally only be used legally ....


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The "steering wheel" is the earth point for the compressor motor --- the switch is to change from " blast" ( all horns powered) & the option is "musical"  -- illegal I think --- IMO 

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If the horn push is NEG then connected to 86 on the relay then 85 needs a POS connection.

I did have mine connected for spaced sound and together it used to sound great.

I also had the changeover switch from standard horn to Air horn.

The good old days of Pander Police Cars

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The musical air horns on my Mini back in the '70s was great at moving pedestrians out/of the road, or drop into 2nd & spin the wheels a little.

Small tale from those days --- my girlfriend ( now wife ) would also use the mini, solo; & came back one day very concerned about the squealing noise when cornering. Didn't think too much of it at the time, then we were together in the car doing a rapid circuit of a dual carriage-way, roundabout at the end. On travelling round the 'bout she said " there's that squealing noise again.

Good old days -- car was built to " Car & Car Conversions " article for a 998cc A series lump, nothing special in to-days hot hatch market but back then we could keep up & probably out run most other cars. 

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I agree with Foz. You can probably just use the current wiring for your new compressor using it in all together mode. If you are using the donor wiring loom then unless it was from a really low end model of Sierrra, (Horn not on steering wheel) then there is already a relay in the fuse box that is being used, and a fuse. So it would be odd to wire up another relay from the current relay. I attach the Sierra horn circuit diagram, might be of use if you have this loom. You can see the horn relay and the fuse F6 which is a 15amp fuse. 47 is the relay, 48 the horn button. 36 is the cheaper option on some models, horn on the stalk switches and no relay. By the way, the two diagrams that came with the new horns are to cover the two options that could be faced by the installer. The top diagram covers the case where the horn switch provides the power (+ feed) to the horn and the horn is the route to earth(-ve). The bottom circuit is the other way round, where the horn switch provides a route to earth from a horn that already powered from the positive. You will notice that the sierra is using this latter case, the horn switch 48 provides a route to earth.


Edited by Sparepart
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