Getting the horn............to work!!

[mowerman]

Checking bits for the MOT I now find the horn has stopped working  :( Electrics are not my strong point so this is what I`ve found so far.  Having taken off the steering wheel and disconnected the bit that connects the horn button to the slip ring if I short between the steering column and the steering column bracket the horns work, but they will not work using the horn button  :-/ Am I right in presuming that the steering column is live and the horn push completes the earth circuit to operate the horns?  If so I think that the slip ring connector needs looking at. If not, god knows!! Can anyone shed light on Lucas the prince of darkness  :) Thanks, Steve.

[heraldcoupe]

The horn has a permanent live feed, the earth return is via the slip ring. The horn push grounds the slip ring to the steering column, completing the circuit. The column and slip ring should only be connected when the horn push is depressed.
The most popular failure mode is for the steering column to become isolated from ground. There is an internal link wire to the column lower coupling which can fail, with another between the steering rack and the chassis. When the column column wire breaks, the fault is usually intermittent.
Cheers,
Bill.

[Nick Jones]

Unless you are using one of those newfangled universal joint things in place of the original rubber coupling which case it all mysteriously starts working again  ;D

Horn button (standard one) now working for the the first time in 20 years  8)

Nick

[mowerman]

Hi Bill, where you say "internal link wire to the column lower coupling" is that actually inside the column? or am I being dense  :) Thanks, Steve.

[herald948]

There should be visible a (usually braided) wire that literally runs between the upper and lower parts of the column coupling. If you don't see one on your car, try simply taking a piece of wire and bridging the upper and lower parts while someone else operates the horn button; chances are you'll hear the horns, or at least some "clicking" from one or both, after which you can make a more permanent installation.

[heraldcoupe]

herald948 wrote:

There should be visible a (usually braided) wire that literally runs between the upper and lower parts of the column coupling.

The wire isn't always visible. Original coupling often (usually?) have a concealed internal wire to perform the ground function. It's common form to add an external link when the internal wire fails. Some couplings may well have the wire applied externally as an original feature,
Cheers,
Bill.

[herald948]

Good point, Bill. I've a second edition Herald [948] Spare Parts Catalogue that does NOT show anything, but a fourth edition Herald [1200] SPC and a Spitfire 4 SPC both show p/n 110461: "Strip, conductor, on bolt"! According to the Canley Classics web site, the part number now is 130581 for £4.04. (No offense to CC, but I made one far cheaper than that.  :X )

See circle 18 on http://www.canleyclassics.com/catalogue.asp?id=vitesse1600_steering&scale=large