Horn fuse blowing, possible short?

[nifton]

Hi chaps & chapesses,

I know there are a couple of similar posts regarding this, but i think my issue is slightly different.

My horn worked fine until last week, I noticed it wasn't working, and sure enough, found a blown 10 amp fuse, since then its gone through 3 10amps, a 15 and a 30! (tried the 30 just to see if it held the charge, and the 15 because quite a few other cars use a 15, so thought it may be under rated).

When I replace the fuse, the horn works fine, repeatedly. Using the horn is fine, I suspect something shorts when i turn on the ignition.

I can remember rather enthusiasticaly activating the horn at some dizzy bint in a Ford Ka, could this particulaly percusive use have bent a contact or something?
I'm keen to have some ideas before I go messing under the steering wheel cover as I'm quite worried about the airbag charge going off.

[billofdurham]

I can remember rather enthusiasticaly activating the horn at some dizzy bint in a Ford Ka,

Tut, tut. The warning instrument is there to make your presence known, not display your anger at other motorists.

That fuse only covers the horn on your model so we can rule out any other component on the circuit.

You may well have bent a contact but I can't work out how the horn is OK until you switch on the ignition and then the fuse blows. Obviously the horn works with the ignition off so it doesn't rely on the ignition for its feed. Have you tried removing the fuse, switching on the ignition and replacing the fuse? That's what is known as clutching at straws.

The good news is that on your model you don't need to do anything too elaborate to remove the steering wheel. If you would feel safer, you could disconnect the battery negative lead and let the car stand for 5 - 10 minutes before starting work. VADIS doesn't specify this for your car.

440 SRS and horn.pdf

(4.13 MiB) Downloaded 689 times

Bill.

[nifton]

Its very sporadic, it doesn't seem to be ignition current related, today i've been driving for at least an hour without it blowing. Yesterday, it had gone just after I set off.
I assume this is indicating more to a short created by a part of the horn circuit shorting against the chassis at some point, i'm thinking maybe its rubbing on the streering frame.
Will check it out tomorrow.

[billofdurham]

Start at the front with the horn(s). With our current weather any slight break in the insulation will short out.

Bill.

[nifton]

I think I've sorted it, though I cannot say how.

I took the front of the steering wheel off, and cleaned out and dust, ensured the horn conacts where running freely, removed and reconnected all couplings, replaced cover.

Checked under hood for missing or soiled insulation, found nothing.

Dropped the steering wheel, and had a good fiddle with the loom under the cowling, afirming all connectors and making sure there were no rub spots.

Its hasn't gone again yet, and its been two days.

If it goes again, i'm going to have to take the cowling off and have a good visual check.

[billofdurham]

Don't you just love electrical gremlins? As soon as you fix one problem you immediately think the little devils are beavering away to create another.

Keep us posted.

Bill.

[nifton]

Hi Bill, hope you had a good Christmas break.

A quick update on the horn situation;

It started fusing again after a few minutes of ignition a few days after my last post.

I had the horns off and stripped the loom as far back as the interior bay and found a 3inch section of powdered copper core, complete with arcing marks on the beam it was shorting against!

Have now re-run the loom to a less exposed position and re-insulated the entire exterior loom.

I now have both horns working, and have been so for over a week.

I've done alot more work as well, but i'll put that in another thread.

Tom

[nifton]

Oh, and the other gremlin you correctly foresaw which started last week is lamp status on the dash;

Running light, dipped and fog bulbs no longer light up, but full beam does for some reason.

Pretty sure it's a loose connection behind the dash or selector knob, i'll find it though.

[billofdurham]

It's warmer working inside the car so this will be priority now.

Bill.