Horn not working

[1958trebor]

Good evening team, I wonder if someone could advise me regarding a problem with the horn on my 1954 series 2? I took it to work this morning after the usual hibernation and it all went well. However, on the way home, I had to use the horn when someone swerved into my lane and found that it worked for a second and then stopped and appears to have given up the ghost. There is power to both terminals on the horn but no power on the wire which comes from under the dash to the steering column where the copper ring sits. It has done this before but started working again a few weeks later. I can't see where the wire under the dash goes apart from into the loom. Is there some sort of relay in the circuit? it seems weird that there is power to the horn but apparently not to the push. many thanks, Rob.

[svenedin]

There is no relay. The horn has 2 wires connected to it. One is purple (permanent live) connected to one terminal and the other is purple/black connected to the other terminal which is the return to earth. The horn works in a slightly strange way in that it is always receiving the live connection but the switch (the horn push via the slip ring) is in the earth. Well at least that is how it works in my later car. I would have to check the wiring diagram for your 1954 car.

Does that explain some of the weirdness?

You have already established that the horn has power so the fault must be in the earth return part of the circuit or the horn itself.


Possibilities are: 1) Horn not working internally. Usually dirty contact breakers. You could test on the car by leaving the permanent live connected to the horn and connecting to earth on the other terminal. Might want to wear ear defenders! 2) Some failure of the earth part of the circuit. Slip ring not making a good contact, central contact coming up through the steering column, horn push internally or horn push contact to steering column (via the little spiky clips)

Apologies if some of this is not entirely correct for your earlier car but the principle is there......Just a question of testing the horn itself and if it works when earthed you would then have to trace where the fault is by continuity testing with a multimeter. Car electrics being only 12v are very fussy about bad connections with high resistance.



Stephen

[geoberni]

OK, lets keep this simple.
The Horn is controlled with a 'Switched Earth' rather than a 'Switched Supply'. This makes no difference to the horn because all it wants is electricity flowing through it.
It doesn't matter where you open the circuit.

At a really basic level, electricity voltage is a 'pressure' a bit like having water pressure in your pipework at home (the difference it it doesn't go all over the floor if you cut into a cable ).

So taking this sentence....

There is power to both terminals on the horn but no power on the wire which comes from under the dash to the steering column where the copper ring sits.

Power on both sides of the horn is fine, you're measuring the 'electrical pressure' on the terminal into the horn and the terminal out of it. This doesn't guarantee that the horn is OK, but it does mean that it's not open circuit.
However, there should be 12v (or near enough) at the Slip Ring on the Steering Column, because the next thing after the horn is that tab connecting to the Slip Ring. There's no breaks between the 2 points.
Potentially you've either got a poor cable connection at the Horn, or at the Tab.
It might just be that your test meter, assuming you're using one and not a test lamp, had a poor connection to the Tab.
From the Tab it connects to the Slip Ring and then inside the Horn Push where it earths to the Steering Wheel, via the metal log that the fixing screw goes into.
I took these photos this morning, not just for you, I realised I didn't have a photo of the horn open in my 'collection' of car parts photos.
All nice and simple.

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20250401_121159.jpg (1.27 MiB) Viewed 5556 times

[mike1864]

Have you checked the horn button itself? Without disconnecting any wires, try connecting the push button tag that terminates the wire coming up the column to a good earth (eg the column metalwork).
This just emulates what the push button does (or SHOULD do).
If the horn sounds, the push button is broken.

[geoberni]

Have you checked the horn button itself? Without disconnecting any wires, try connecting the push button tag that terminates the wire coming up the column to a good earth (eg the column metalwork).
This just emulates what the push button does (or SHOULD do).
If the horn sounds, the push button is broken.

He's said there's no voltage at the slip ring.
Now that might just be a poor connection of his Meter; but if there's voltage leaving the horn, it should then be at the spring connection to the slip ring as it's a straight cable run from one to the other.
Probably the simplest circuit on the car.
Likely just needs to clean the connections, unless the wiring is rotting and damaged somewhere else.
Only he knows the condition of the wiring.

Horn.JPG (136.02 KiB) Viewed 5411 times

[mike1864]

Just to eliminate a measuring issue, how about shorting the slip ring to chassis, and letting us know if the horn sounds?
Otherwise I'd check (re-make) the connector on the cable coming from the horn towards the slip ring. Maybe just one strand touching; hence the reported intermittency.

[1958trebor]

Hi, thanks for the advice. I worked through it and the horn has started working again. I can't say I'm absolutely sure what it was but cleaning, tightening and generally wiggling things appears to have done the trick. Many thanks!

[svenedin]

Excellent! Parp parp.

[geoberni]

Good stuff.