Help needed please pdq on electric horn….

[Denis Sweeney]

Just carrying out last checks on my ‘36 ARQ Ruby prior to the Eurotour next week, we leave for Dover on Monday, but out of the blue the electric horn seems to have given up the ghost.
It looks like a “Lucas Altette” type but has no visible outside makers marks to confirm its origin. The horn was with the car when purchased in 1984. It is like the high frequency type shown in the companion.
Have checked continuity on all wiring to and from horn push on the steering column to the junction box and on to the cut out unit and thro to the horn unit itself with a circuit tester and all appears ok. 
Have checked all fuses and cleaned the horn push area with brake cleaning fluid and a brush. 
Then checked the earth connection and this failed, result I thought, but having now established a good earth to the unit, again tested with the circuit tester, the horn still remains silent.
Any ideas as to what the problem inside the horn could be would be helpful, or any ideas on a quick cheap replacement to have as a temporary fix to make Ruby road legal for the trip would be very much appreciated.
Cheers

[GK5268]

If it is similar or is a Lucas Altette, then if you remove the nuts holding the two halves together it will come apart, inside there will be contacts, probably just need to clean these and all will be well again. Good luck.

[John Cornforth]

Hi Denis

The horn doesn't have an earth, it sits on the "live" side of the circuit. The horn push switch does the earthing (to the steering column), so both terminals of the horn are isolated from its body. The body may well be earthed via its fixing bolts, but this plays no part in its operation.

[Denis Sweeney]

Just shows what I know…..

[Graham Barker]

I am going through the same thing with the horn on my Ruby. To be certain whether the problem is the horn or the  wiring, I tested the horn by running wires directly to the horn from the battery.
Hope you get resolution of the problem quickly. 
Regards 
Graham.

[Denis Sweeney]

Thank you to Gary and Graham all good now.
Did wire the horn directly onto the battery and it did bleat very timidly, but it was better than nothing at all, so in the end stripped the horn down and cleaned up the contacts with 1000 grit W&D and made sure it all went back in the correct order.
Getting setting of the armature took a lot of trial and error but all good in the end, horn is now many decibels louder than it ever was. Result.
Could not find any makers mark anywhere on the unit, although there was a recessed area on the rear of the horn body, where you might have expected to see an inscription of some kind or a label but that had long since gone.
Thanks again

[Bob Culver]

From the post wording i thought perhaps it would not stop....
One of my cars developed an intermiitent earth whilst parked. When I went to drive home at end of day a couple of locals advised me of their disrupted day....

[Graham Barker]

The horn on my Ruby stopped working. A replacement horn worked when connected directly to the battery, but wouldn't work when connected into the car wiring system. After cleaning the horn button contact with brakeclean and rubbing with fine sandpaper, still no sound from the horn apart from a clunk. 
The wiring seemed OK.
The next step was to curse whoever thought of using the vehicle body as the return wire in an electric circuit. Where could the poor connection be? There were several places that connection could be poor. 
I decided to eliminate these with two modifications. 
First I connected the brass tang of the horn button contact to the flange of the inner tube of the steering column. See photo. It didn't cost anything, just cut a strip from a baked bean tin.
Second was fitting a clamp on the bottom of the inner tube where it protudes from the bottom of the steering box by about half inch. This was made by cutting down a small battery terminal clamp. From this clamp I ran a wire to where the battery earthing lead connects to the starter. 
Hence a reliable return circuit for the horn. 
It's not pretty, but the horn now works well.