Horn Wire Column

[zippy500]

Hi,

The horn doesn't work, I,ve narrowed it down to the wire running down the steering column, but for the life of me I cant see where it pops out under the car, could someone please explain what/where I should be looking!!!

Cheers

[bmcecosse]

Look at Barry's wiring diagram http://www.mmoc.org.uk/index.php?name=P ... ic&t=19679 and you can see it's a purple wire that comes FROM the horn and is earthed on the column to complete the circuit and make the horn sound! That purple wire is live all the time - to and from the horn. It runs in the loom and comes from the non-ignition fuse on the fuse box.

[rayofleamington]

in answer to your question, the wire to the horn switch that runs down from under the horn switch 'comes out' next to the indicator switch (- or next to where the indicator switch would be on the column if you don't have one)

The end of the wire that comes out of the column is hidden. With the column shroud removed, you should see a yellow metal ring sitting on a plastic collar on the column shaft. The wire contacts the underneath of the metal ring.
There should be a 'brush' on a springy arm contacting the metal ring. (the springy arm is not extremely springy so will take a permanent bend if you are not careful with it)

This type of 'brush' is called a brush for historical reasons and can be mainly carbon or copper or other soft metal (in some cases it's made from metal strands but I've only ever seen that on scalectic cars)

This may see a bit off topic, but it's actually not - the slip ring on the column and/or the metal brush / springy arm are the amongst most likely culprits when it comes to horn wiring.
(the other likely culprits are the horn itself, the connectors at the horn and the live feed to the horn)
BE's comment is correct - the horn circuit earths to the column when you press the switch.
i.e the live runs to the horn and back to the dash, across the brush/slip ring and up the wire to the switch. The switch completes the circuit by connecting it to the column shaft (earth) when the button is pressed.

Don't be tempted to use a volt meter when checking the slip ring / brush contact! This is one of the cases where you should use a bulb tester. The slip ring can appear live when in fact it has a very high resistance contact.
If you can light up a bulb when connected between ground(-) and the slip ring(+ve) then that part is fine.

To get the column shroud off, you need to remove the steering wheel. To remove that the nut is under the switch. You need a 33mm socket (or the correct non metric size). Typically you'll see chisel marks on the nut when it had been removed / fitted without the correct tools. I used the chisel method when 20 years ago before I was out of my teens and on a non existant budget, but these days would consider jobs like that an opportunity to get the correct tool...

The top of the wire sits in a clear plastic housing which is spring loaded. The assembly can be dismantled by removing the circlip from the connector on the wire end.

[zippy500]

Thanks for your answers.

Thanks ray, you were right, I took the steering wheel off and the shroud,
the indicator arm assembly had come lose, so the slip ring wasn't making contact. Once tightened up horn now work. Problem solved

I thought the wire ran direct down the and popped under the car

One think less to worry about for the MOT on Tuesday

Cheers

[rayofleamington]

the indicator arm assembly had come lose, so the slip ring wasn't making contact

Well done for sorting it - I've seen some where the brush was missing (worn off or broken off), and that's more of a pain to sort.