Evening all. As above, my horn fuse keeps blowing and I am rather stumped as to why. It doesn't use a relay, but it is a very quiet motorcycle horn (enough for an MOT, but not really to warn people with!). It has worked fine (all be it quietly) for the last 2000 miles. Now, it has blown the fuse, and I can't see why. If I hotwire the horn, it works just fine, but as I am mid way through a house move, I have very limited tools (no multimeter). Can anyone give me some ideas as to what could be causing it? It had a 10amp fuse (I naughtily tried a 15 amp to see what happens, and it blew that too!). Any help, greatly appreciated.

To be honest, I am tempted to leave it, as everyone can hear my car a long way before you can see it, so the horn is kinda academic - the problem is it also supplies the indicators, so a blown fuse leads to hand signals, which isn't ideal!

you never miss a horn til you really need it.

Most horns ive seen need 30A fuses? Yours sounds just like it needs a bigger fuse.

Problem with the indicators ?

Dodgy Earth ?

does it blow with the horn disconnected ? or when you use the indicators ? your gonna need a meter and check for isolation of your wires or volt drop testing is a good method (what you see is what you are loosing).otherwise its guess work unless you can spot a chaffed wire anywhere with a visual once over.

Short inside the steering wheel horn push did ity on mine, same symptom.
stayed like it for 3 years til i had to have an MOT till I looked to fix it and found it1!

Indiators seem to work fine once the fuse was changed. Just seems odd that it worked all this time, then all of a sudden it doesn't. The joy of the kit car I guess...!

I will try disconnecting the horn and seeing if it still blows. Good plan batman. I will have my trust multimeter by Monday, so the investigation may have to wait until then otherwise. Thanks for the pointers chaps.

Is it a sudden thing, or a 'worked in autumn bit not noe ive got it out the garage'


Daniel

steering wheel center horn..had loads of issues with mine earthing....

It has worked with no issue, until a drive the other day. It has worked as recently as last week.

I would suggest youve got a direct short somewhere.

Its possible nay probable that there has been a wire chafing and now its gone through the insulation and touching chassis giving dead short

quote:

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Originally posted by JoelP

Most horns ive seen need 30A fuses? Yours sounds just like it needs a bigger fuse.

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What thickness of wire are you using to drive the horn? If it's a bit thin and/or a bit long then maybe you're losing some voltage and the horn can't operate properly. If it doesn't pull back enough then it may be holding 'on' too long, which will increase the current. When you wire the horn directly to test, do you use thicker wire, and is the wire much shorter?

I've often seen wiring manuals that say that heavy gauge wire should be used for horns, even if the actual current is quite low, to reduce voltage drop.

Try putting a meter on the horn connector (with the horn still connected) and press the horn button - you should see very close to full battery voltage.

Afterthought - also make sure that the earth connection is very clean and solid, for exactly the same reason.

[Edited on 1/5/10 by David Jenkins]

Sorted - thanks people. It was a short inside the horn push/adaptor. It seems to be louder now too (still don't hear it over the exhasut though!).