New horn needed - wiring help!

[MiniNinjaRob]

My 940 horn is now defunct. They are mounted in an awful place, collecting all the water and salt they can.

I want to fit some Hella Supertone horns. Do I need a relay or not? I have no idea. I also have no idea how I would wire it in, I've looked at some diagrams and it shows a connection to the battery - how do I do this?

I really am a numpty with car electrics so need a step by step idiots guide!

[Michaeleff]

I have a box of Hoens Rob!



I'll send Jock round with a couple....

Wiring?

Simple; connect the existing horn wiring to the out side of the relay and the new power feed to the coil.

But hang on!

Why would you need a relay?

If you simply replace the defunct units with similar, then relay not required or necessary.

Try these for example:

here:

[Laird Scooby]

The horns are already wired through a relay, you could even replace the normal horns with air horns without needing to add an extra relay.

[Alasdair1]

I agree you shouldn't need a relay for electric horns. I had a triple set of air horns fitted to one of my 940. The kit came with a small relay. It was for the air compressor as it was fairly powerful. Sounded a bit like a small lorry. Great for getting folks attention!
I also rewired the horns so they were in behind the front grill pointing slightly downwards. A much better place as they don't get splattered with water and salt as much.



Alasdair

[Laird Scooby]

Originally Posted by Alasdair1

I agree you shouldn't need a relay for electric horns. I had a triple set of air horns fitted to one of my 940. The kit came with a small relay. It was for the air compressor as it was fairly powerful. Sounded a bit like a small lorry. Great for getting folks attention!
I also rewired the horns so they were in behind the front grill pointing slightly downwards. A much better place as they don't get splattered with water and salt as much.



Alasdair

That's exactly what i'm planning on doing with a set of twin air horns, won't be using the little relay that comes in the kit though. Almost always these are only rated at 30A, the Volvo horn relay is 40A if memory serves correctly.

[MiniNinjaRob]

Going to get this one. https://www.amazon.co.uk/gp/aw/d/B01...NwL&ref=plSrch

[Alasdair1]

When I wired the airhorns I kept the standard horns as well. Hence I used the small relay with a fused spur from the battery. I Put an isolation switch on the dash so I could switch the air horns on or off. They were pretty loud so wanted to be able to silence them at night and just use the standard horns. Was a bit paranoid re MOT due to the volume as well.

Alasdair

[Laird Scooby]

That would work well and give you "Town & Country" horns into the bargain!

[Rversteeg]

The horns get a permanent 12V feed and are engaged by grounding the horn via the contact in the steering wheel. The horn has two wires and the ground wire should not be connected directly to the mounting bolt as this will permanently sound the horn.
If I would install a more powerful horn than standard I would connect it via a relay and not let all the power run through the trailing contact ring in the steering wheel.
Usually horns are permanently grounded and sounded by putting 12V on the feed wire. You need a relay to achieve this:
Use the permanent 12V wire (yellow, originally powering the horn) to power the relay (85 and 87). 86 is for the switching wire (blue/black) to the steering wheel. Connection 30 on the relay can now be used to sound the new horn. Extending the yellow and blue/black wire allows you to mount the relay and horn in a less vulnerable place.
You do not need an additional fused feed.

[RollingThunder]

Originally Posted by Rversteeg

The horns get a permanent 12V feed and are engaged by grounding the horn via the contact in the steering wheel. The horn has two wires and the ground wire should not be connected directly to the mounting bolt as this will permanently sound the horn.
If I would install a more powerful horn than standard I would connect it via a relay and not let all the power run through the trailing contact ring in the steering wheel.
Usually horns are permanently grounded and sounded by putting 12V on the feed wire. You need a relay to achieve this:
Use the permanent 12V wire (yellow, originally powering the horn) to power the relay (85 and 87). 86 is for the switching wire (blue/black) to the steering wheel. Connection 30 on the relay can now be used to sound the new horn. Extending the yellow and blue/black wire allows you to mount the relay and horn in a less vulnerable place.
You do not need an additional fused feed.

Exactly what I was going to point out! I found out the hard way a few years ago when I replaced the horn on my last 940 Classic - I nearly jumped 6 feet in the air when I connected the wires up. I was NOT expecting it to be a permanent live feed