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Intermittent horn fault


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No, I'm not talking about episodes of impotence ...

Some while ago, I beefed up my horn by running a positive wire from the battery to a LOUD horn (nautilus type) via a 20A fuse and 20A relay, then switch the relay via the old horn circuit.

This was working fine for about a year, then the fuse went pop (I don't know why - it just did). So I replaced the fuse and again it worked fine. Then the horn started to give out so I replaced it. It continued to work fine for another year, recently went through MOT OK. Then, suddenly a few days ago, I went for the horn button because some stupid twunt cager had jumped a red light ... and the horn didn't work! I pulled over, pressed the horn button a few times - and it worked perfectly. I got home, tried it again, and again it worked perfectly.

I have been a little worried about it since then and today, I again needed to use the horn in anger, and again it did not work!!!! I tried it a few times on the way home and it wasn't working at all. "Aha!", I thought. "Now it's not working at all, I can track down the problem and fix it".

So, I got home, got out the DVM, all the tools, etc, went to try the horn and ... guess what? The f**king thing worked f**king perfectly! So I swapped the horn over for one I know works, tested it, it worked. I took it out for another spin, and guess what? The god damn horn DIDN'T bloody work! I stopped at the side of the road and, nope, not working. So I took it back home again, got ready to diagnose the fault with all my kit at hand and, guess what? The absolute f**king vicious bast*rd f**king horn worked god damn perfectly!!!! :evil: :evil: :evil:

I think it must have a mind of it's own - when I really need it - it doesn't bloody work. When I go to test it - the fault just vanishes into thin air.

Sorry for the excessive swearing, but this has pissed me right off! It's the whole "intermittent" thing - it is driving me NUTS!!! I have tried it with the engine off, engine running, engine hot, engine cold, engine running and rear wheel going round quickly/slowly, indicators on/off, etc, and I just CANNOT reproduce the fault when I have all my testing kit to hand.

I am loathed to take it to my LBS because all they'll say is, "well, we played around with it for an hour and couldn't find anything wrong with it". I will then take it away and, quite promptly, the damn fault will be back. I just know it.

The only thing I can think of doing is ripping out the entire circuit and starting again. Any other ideas?

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see I was going to suggest moving your horn but then I read that you have already upgraded it

the reason been is that on my bro's SV his horn would stop working when it got hot then once cooled it would work fine

we moved it and now its spot on

but you have already replaced it!!

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As above, I think the switch is probably the best place to start.

I've had a couple of intermittent faults in the past week. One was due to a short and was blowing the fuses, other was a loose connector between the main and sub harnesses, which is now cable tied together :lol: )

Aaanyway, you've ruled out it being the horn itself, so thats good.

If I were you, I'd start with the switch. Take it apart, clean it with WD-40 and check its making a good connection

From there, I'd look/wiggle the connector where the horn connects to the main harness

If you still have no luck, I'd start looking at ground points on the bike, making sure everything is clean and tight.

Thats just me though, and its important to note that I have no electrical qualifications and only simple knowledge from diagnosing and fixing a small amount of faults on my own bikes

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