Irregular horn

[Lee T]

Hi Steve, hope your well. Thanks for your suggestion.
I did as you advise when I fitted the twin horns. I replaced most of the wiring from horns to multi plug and continuity tested them. fitted new plugs at horn end. For the time the horn is silent with the fuse in place, the horn operates normally from both buttons and from the donor set I fitted for elimination purposes. 3mns at most and it's off again. Puzzling isn't it.
I havn't tried Simon's coupler idea yet, been a bit wet here.

Lee.

[SD1too]

Hi Lee,

On page 12.4 of Haynes it's said that the horn buttons wiring on the steering wheel is combined in one harness with wiring from the radio remote and cruise control switches. All those connections terminate in a single connector at the top of the wheel (photograph 4.10).

If you haven't already done so, I would check that wiring carefully for insulation damage which could result in a short to earth.

Simon

[Lee T]

Yes that is true Simon. I have a spare set of horn, cruise and radio buttons that have been fitted for testing. I have another set in a spare steering wheel, may fit that as a last resort test. Not much else left on the elimination list now, Relay, coupler or random fault no one has experienced before. Will be fault finding today, so will update the thread later.

Thanks. Lee.

[Lee T]

Removed the steering wheel, everything surprisingly clean behind for a 20+ yr old car. Unplugged the white plug at back of clocksprings and finds what looks and smells like brake fluid coating the plug and on the wiring.
After three lots of electrical contact cleaner on, in and through everything with 15mn intervals, I reassembled.
RESULTS.
Horn still sounds as before, only now if I use either horn button it will sound continuously, before it operated normally from the buttons before sounding continuously.
No Idea how brake fluid could have got there but if that's what it is I may have my answer. As brake fluid is a corrosive I would expect to see damage to the wiring or the plug pins, but pins are clean and wiring fine. So I'm left with another mystery, and a new twist in the problem.

[SD1too]

Originally Posted by Lee T

Unplugged the white plug at back of clocksprings ...

Is that the white connector which I mentioned in post no. 6?
If so, did you perform the test I described; unplugging it then reconnecting the battery? If the fault then clears it will confirm that the problem lies at the steering wheel.

Simon

[Lee T]

Yes the white 6 slot connector, next to the yellow airbag one. I did try it unplugged and that test along with the fluid and the new addition to the fault confirms the source of the problem I think. So unless the cleaning spray has had some miraculous overnight effect, I require a replacement coupler.

Thanks. Lee.

[SD1too]

Thanks for the progress report Lee.

You can confirm your suspicion by taking the white 6 pin connector (C0082) female side and, using a temporary link, join pin 1 (purple/black wire) to pin 6 (black). The horn should sound immediately and when you remove the link it should fall silent.

This test by-passes the rotary coupler and steering wheel horn switches. As you have ruled out the latter by substitution, it effectively puts the rotary coupler in the witness box.

Simon

[Lee T]

I am attempting to source a replacement coupler, once aquired I will remove everything again and try bridging the pins. I think I have my answer to be honest, given the mystery liquid that smells like brake fluid and the fact cleaning it only changed the problem, I'd rather go back in armed with a replacement part. If I am wrong the search will continue anyway and I will have a spare coupler. Thankyou for your help and advice. I will update the thread once I have a confirmed result.

Lee.

[Lee T]

SOLVED
New coupler arrived today.
Thankyou Andy (Sir Trikealot). Thankyou Simon for your helpful posts.
Fitted 3 hrs ago and not a peep nor a beep from the horn unless buttons are pressed. So normal service resumes and car is 100% problem free, for now at least.
As for the cause, short of a Crime lab I can't be 100% sure. I'm pretty convinced it is brake fluid. As for how it got there, I have no idea. Ive owned the car 10 yrs, I do my own maintenance and repairs, it is left with same trusted garage for MOT only, every year.
Lee.

[SD1too]

Hi Lee,

Thanks for posting the result of your repair which is great news.
Shall we just reflect upon our conversation earlier in your thread?

Originally Posted by SD1too

What about the rotary coupler? In the wiring diagram this carries both legs of the horn switches which makes it worth checking for a short circuit.

Originally Posted by Lee T

I did consider the coupler but have never heard of one failing and cannot find any posts detailing failures. So I assumed the relay ...

Originally Posted by Lee T

SOLVED
New coupler arrived today ... Fitted 3 hrs ago and not a peep nor a beep from the horn unless buttons are pressed. So normal service resumes ...

It just goes to show doesn't it that unlikely though it sounded, a component that you didn't believe could be responsible, in fact was the culprit!

Every day is a school day with car maintenance.

Thanks again Lee for your appreciative comments.

Simon