Horn Not Working - Wiring Help?

[Altrezia]

Hello chaps.

Sorry for yet-another-stupid-question from me, but I'll be done soon.

My horn doesn't work. I've checked for power at the horn itself and there's nothing there (well, 0.4v..).

I have an aftermarket steering wheel, but there is a lose wire inside. When I touch it against the base of the wheel I can see a tiny blue spark, and I can hear a feint click from the relay (I presume) - but no horn sounds.

Three questions:

1. What wires on the steering column are for the horn - I presume if I was to wire in a button for the horn it'd be one wire and the other side to an earth point?

2. What relay/fuses are for the Horn - I think it's on this diagram, but I'm not sure how to check a relay, tbh. Can I swap it with any of the other's to check?

3. If the relay is good, and the wires on the column are working as I expect, what else should I check to get the stupid horn working?

(Urgh.. who uses a horn anyway?)

Thanks again!

-a

[Grrrmachine]

You need to tell us what car you have, as horn systems aren't standard across the E30 lineup.

What you are missing from your checklist is testing the actual horn itself. Horns get exposed to road dampness and salt, and often corrode up, so checking the horn on a known working power source (car battery?) is a good place to start.

[Altrezia]

It's a 1990 320i, a UK car.

Horn looks OK, but not getting any power at the connection to it.

[Brianmoooore]

Sounds like you have two faults. One in the control circuit of the relay (the loose wire in the steering wheel), and one in the circuit controlled by the relay (probably the horn(s) itself/themselves - I would expect your car to have two horns).
Fuse for the horns is #7, and for the control circuit, #6.
To 'test' a relay, pull it out and use a short piece of wire to link together pins 30 and 87 of its socket. Pins are marked on the relay itself.
This should make the horns sound continuously.
As for who uses a horn; I do, at least half a dozen times every time I leave home. Horn is as essential as brakes around here.

[Altrezia]

Well the steering wheel thing is easy to sort but I had hoped it was just that, you know?

I'll check the relay tomorrow. The fuses all look OK.

Everything is in the one fusebox in the engine bay, right?

Thanks for the help

[Brianmoooore]

All conventional fuses, except one, are in the fusebox on an E30.
It's no good checking for power anywhere with a meter. The best 'tool' to use is a 12 volt bulb of about 5W, attached to a couple of pieces of wire. Most of my automotive electrical fault finding is done with an E30 indicator repeater lamp with the plug cut off.

[Altrezia]

Sorted.

You were right - the horn is fubar, and the wiring was dodgy. Sorted the wiring, tested with a voltmeter (sorry) and just need to order a new horn.

Thanks

[Brianmoooore]

Where is the horn on your car?
A meter takes an extremely low current to work it, so when a fault with a resistance of tens of thousands of ohms is present a meter may still give a voltage reading only slightly less than expected.