Help fitting new horn, please

I have fitted a new horn physically, but am now stumped by the wiring.

There appear to be two 12V+ wires going to the OE horn, with the 12V- being supplied by the fixing bolt. Can anyone enlighten me. Also, do I need to fit another relay and/or uprate the fuse, or will the OE bits do? The new horn is just a dual tone one, so nothing too heavy for the wiring...

The Jimny's electricals are ground switched, meaning you have a permanent +12V and the ground wire (negative) is connected when needed. So that's why you have two wires: one is permanently live, the other one goes to ground but it's only connected when you press the horn button. The car body is indeed a ground point also, but it's permanent; cannot have the horn sounding constantly

The default horn is rated at 4A (it's a motorcycle horn, actually, not kidding); most of the "real car" horns are using more than that. I've also replaced my horn and the new one said it draws about 12A, so I've replaced the original horn with a relay and supplied power directly from the battery.

Old setup:

--livewire----> (horn) <

---

grounding_wire----

New setup:

--livewire----> (relay pins 85,86) <

---

grounding_wire----
----fused_wire_from_battery----> (relay pins 30,87A) <

---

wire_to_horn----> (horn) <---grounding_wire----

When you push the horn button, the relay closes and supplies power to the horn. No mods to the original car wiring, easy to switch back if desired, can reposition horn if desired (I've put mine behind the headlamp, as it was quite exposed in the original position and the new one didn't fit there anyway).

Many thanks, that's really helpful information. I have owned about 25 cars in my time, but negative switched electrics is a new one on me

...as is a motorbike horn on a car - that explains why it's so weedy!

Welcome! Yes, the stock horn is quite feeble and that's probably the reason for mounting it so "open" behind the grill: to be heard ! when I took mine out it was already beginning to corrode.

The negative switched wiring was a surprise for me also, but after thinking a bit it's quite clever actually: it's much easier to find and connect a grounding point when needed rather than pull a wire each time for bringing +12V to your gadget. Clever clever.

VAXXi wrote: Welcome! Yes, the stock horn is quite feeble and that's probably the reason for mounting it so "open" behind the grill: to be heard ! when I took mine out it was already beginning to corrode.

The negative switched wiring was a surprise for me also, but after thinking a bit it's quite clever actually: it's much easier to find and connect a grounding point when needed rather than pull a wire each time for bringing +12V to your gadget. Clever clever.

Earth switched horn is quite common in fact I think it's pretty much standard. I think the reason might be the centre of the steering wheel button, much easier to switch an earth (just make contact with the steering column) than have a live wire there all the time as it'd be more likely to get broken or short out, there again maybe I'm speaking Bo*****s again!!
John.

Have had my Jimny - 57 plate - two weeks now and have just replaced the parpy horn. I am not sure whether the standard wiring has changed but there wasn't a live feed to the horn. I disconnected the two wires to the horn and testing with a lamp the white wire was live when horn button was pressed. Black wire I guess goes to earth.
Fitted a relay where the old horn came out and connections as follows...
86 - white wire leading to horn button (disconnected from old horn)
85 - Black wire from old horn
30 - Live - took a feed direct from the battery with a 15A inline fuse holder
87 - to new horns - mounted on chassis behind bumper

One thing I did need to do was put an earth from the new horns to the body. The chassis didn't provide a good earth connection, I guess due to being separated from the body by rubber bumpers.

Ray