Horn stopped working

[DWW]

Came to use my horn today and was greeted with total silence, stopped working just like that. Any clues where to start diagnosing the issue. The most likely is probably a wire coming loose but where, is the question. Any help welcome.

[rswaffie]

Hi
Do you get a click at the relay? If not, check the wiring at the relay and from there back to the fuse (and the fuse). If you do get a click, then it’s going to be more work as from memory you can only access the horn wiring via the headlight voids - so the scoops will have to come out to get to the horn connections and the multi-terminal block.

[dlgis]

Mine wasn’t working so i ran wires to the horn relay from the battery and was treated to a nice healthy horn blast. I did try another relay but it turned out to be a dodgy connection. It was my mate found the problem so I can’t tell you exactly where. I did also clean up the big plug that connects to the bonnet just in case. Basically i had a lot of electrical problems and most were down to poor connections and a few duff switches.

[Jeremy]

Forgive me Danny when I ask, did you check the fuse? I only mention it because I blew my horn fuse when I did about 3 quick toots on my horn to point out to another motorist that he'd been driving down the motorway with his indicator permanently on. I know the horns take a big current and perhaps there's a bigger spike when contact is first made. Perhaps also my fuse was a bit dodgy.

[DWW]

Thanks Jeremy, no I haven’t checked anything yet but for obvious reasons the fuse will be my first port of call followed by the earth wire on the steering column and then the rest relay and engine bay wiring. Thanks for all for the advice given.

[DWW]

Ok, ran a few tests, firstly the 50A fuse was blown marked HORN, replaced it and as soon as I pressed the horn
it blew straight away. The other fuse which supplies the low current side of the relay is fine. When I fed 12V to the horn relay contacts the horns operated fine. Had to leave it there since I ran out of 50A fuses anyway. Any clues?

[DWW]

Update:

Thought the horn relay was faulty fitted a new one and the horn worked. Took the car for a test ride tried the horn nothing, checked fuse 3 and of course it was blown. Seems one of the horns may be faulty/shorted? When it did worked work for a short while it emitted a single tone only. Am I on the right track?

[bitsobrits]

You are getting close! If a fuse is blowing, and you have a known good relay, you have a short to ground somewhere in the positive feed to the horns from the relay.

The wiring to the horns in the early bonnet mounted horns just sort of lays in the front bonnet pan and over time can wear away the insulation from moving about. It's a bit of a pain to replace it, or even check it, but if the voltages at bonnet plug all check out, then you will want to look at the bonnet harness.

When I rebuilt my car I removed the front harness for inspection and a couple repairs and re-installed with some shrink tube over the long run between sides to reduce future chafing.

[chrisfell]

The few times mine has stopped working it was only one of the two tones. That made diagnosis simple - it had to be the non working horn or its wires. Took it off, connected it to a slave battery, nothing. So it taped it with a small plumber’s screwdriver (), and it worked. I’ve done this twice more since. Next time I may have to strip the horn units and remove the rust from inside.

[DWW]

Will check all the above tomorrow, thanks.