Thread: 2a Horn Troubles

Originally Posted by FM97

I cant seem to get my 2a horn working.
I did my best to follow the steps outlined in a previous thread
link: http://www.aulro.com/afvb/series-ii-...s-2a-horn.html
but still cant get it to work.

Can anyone help?
I tried to clean the copper contacts best I could.
Pictures might help diagnose.


<I can't see the Brown/Black lead from this contact ring back to the wiring harness. Is it still connected? >


<From memory this contact arm is supposed to be essentially straight, not doubled over as in this pic. It then has to have sufficient tension to run on the ring.>

<image removed>

Now there are a couple of things you need to sort out and it may be best to go back and check everything one by one.

Does the horn actually work?

There should be two wires leading to the horn.

1. A brown wire. This should have constant power.
2. A brown wire with black stripe. This goes to chassis ground via the horn button.

Test the horn, by bridging the terminal with Brown/Black directly to the chassis of the vehicle. The horn should sound.

If it works, connect everything back as it originally was.
If it doesn't work, check that there is power on the Brown wire with a test lamp.
If the there is power but it still doesn't sound swap the wires to the opposite terminals and re-test.
If it still doesn't work, replace the horn.

Once you know the horn works you can trace the problem back up the wiring.

With your test lamp, the lead grounded, test that the Brown/Black wire coming out of the harness near the steering column, has power (or just ground it and the horn should sound.)

If there is no power or the horn doesn't sound. There is a break or disconnection between the horn and the steering column harness.

If everything works to that point, your problem is in the button or contact ring.

Test the button. A multi meter on continuity works best check between the ground lead (Black wire) and the connector on the back of the button. You should get continuity when the button is depressed and not when the button is in its normal non-depressed state.
If you get continuity, your problem is in your contact ring. (Or connections.)

The connections,

1. The black lead on the horn button connects to the copper terminal that is bolted under the nut on the steering wheel.
2. The terminal under the centre of the horn button, connects to a Brown/Black wire with bullet connector that comes from the contact finger.

Yeah just see if you can make it go manually.

I know on my modded 2A someone had put a big ass (glass cover) relay in between the steering column and the horn itself (located in the front right of the engine bay). I guess they used to have a bigger horn or something?. This made things harder as it was then a live wire being relayed to the horn which was grounded to the car.

It was a bit of a headache to sort out. Ended going back to the horn, ran 12V straight to it to see if it worked, then found each junction and tested it from there, Until i realised it was just a bad wire from the horn button not grounding correctly..

Originally Posted by ozeraser

Yeah just see if you can make it go manually.

I know on my modded 2A someone had put a big ass (glass cover) relay in between the steering column and the horn itself (located in the front right of the engine bay).
...<snip>.

It is not uncommon to fit a relay into the horn circuit. Not usually a big ass (glass cover) one though, usually one of the small box Hella/Narva type.

The reason is that it can operate efficiently even with a poor contact from the button/slip ring mechanism. In the usual Prince of Darkness - Lucas/Rover design the entire current to sound the horn runs through to the button and will arc and carbonise the contacts. A relay allows full current for the horn and very low current through the button, making everything more efficient and reliable in the long term.

It is the same with headlamps, (particularly on SIII models with plastic switch mechanisms).

Originally Posted by Lotz-A-Landies

Now there are a couple of things you need to sort out and it may be best to go back and check everything one by one.

Does the horn actually work?

There should be two wires leading to the horn.

1. A brown wire. This should have constant power.
2. A brown wire with black stripe. This goes to chassis ground via the horn button.

Test the horn, by bridging the terminal with Brown/Black directly to the chassis of the vehicle. The horn should sound.

If it works, connect everything back as it originally was.
If it doesn't work, check that there is power on the Brown wire with a test lamp.
If the there is power but it still doesn't sound swap the wires to the opposite terminals and re-test.
If it still doesn't work, replace the horn.

Once you know the horn works you can trace the problem back up the wiring.

With your test lamp, the lead grounded, test that the Brown/Black wire coming out of the harness near the steering column, has power (or just ground it and the horn should sound.)

If there is no power or the horn doesn't sound. There is a break or disconnection between the horn and the steering column harness.

If everything works to that point, your problem is in the button or contact ring.

Test the button. A multi meter on continuity works best check between the ground lead (Black wire) and the connector on the back of the button. You should get continuity when the button is depressed and not when the button is in its normal non-depressed state.
If you get continuity, your problem is in your contact ring. (Or connections.)

The connections,

1. The black lead on the horn button connects to the copper terminal that is bolted under the nut on the steering wheel.
2. The terminal under the centre of the horn button, connects to a Brown/Black wire with bullet connector that comes from the contact finger.

Thanks for the response, the black contact lead is attached, it just cant be seen in the picture. I suspect its a wiring issue and not the horn itself that's gone bad. Ill have to pick up a test lamp on the weekend and try and fix it. Ill hopefully have it fixed by Sunday.

Originally Posted by FM97

Thanks for the response, the black contact lead is attached, it just cant be seen in the picture. I suspect its a wiring issue and not the horn itself that's gone bad. Ill have to pick up a test lamp on the weekend and try and fix it. Ill hopefully have it fixed by Sunday.

First thing I'd check is the folded over contact finger. 2nd pic.

Originally Posted by Lotz-A-Landies

First thing I'd check is the folded over contact finger. 2nd pic.

I had a quick look on ebay. Think this is what it should look like, hopefully bending it back will fix it.