10 replies to this topic

[beardylondon]

Mk1 Mini Super Deluxe
1966
Mota-Lita steering wheel with after market boss

hi all,

I have a fault with the horn push on my Mk1 mini. Its been working fine for 10 years and now doesn't work.

I have taken off the steering wheel and can get it to work by putting a screw driver between the central spindle and the collar, but it wont work when making a circuit with the wire pointing out the end (which the horn button meets).

I'm guessing the wire is damaged internally in the steering column, as there was an intermittent fault which would cause the horn to sound if you knocked the steering wheel too hard.

sounds like a steering column out job perhaps?

Edited by beardylondon, 06 February 2010 - 04:05 PM.

[dklawson]

It has been a while since I've worked on my car's horn circuit so the following is largely from memory and I apologize if I state something incorrectly.

With the stock hub, there is a slip ring on the outside of the column. That should have a connection to the purple/black wire that goes off to the horn. The pushbutton should connect that slip ring to the column itself to provide a path to earth for the horn power. The horn itself will be receiving a constant live feed via its purple wire.

Therefore, any intermittent horn sounding when you knocked the steering wheel could be a problem with the horn pushbutton itself, the slip ring, or the connection between the hub and the slip ring. Any one of these could accidentally be creating a short to earth allowing the horn to fire. It is very likely that you'll need to pull the steering wheel hub to determine where the fault is.

My car has a period Monza wheel by Sparco. I was having problems with the horn pushbutton itself. No matter how I cleaned the contacts, they were not suitable to carry the horn current directly. I added a horn relay to the circuit and this addition changed the requirements of the horn pushbutton. The contacts now only have to pass the few milliamps required to pull in the horn relay. My horn has worked much better in the years since. Yours may also benefit from the addition of a relay.

[beardylondon]

hi,

thanks for your feedback, I'm not sure if we are talking about the same things, so to make things easier Ive taken a picture and labeled it.



Basically if I connect A and B together the horn works.

If I join A and C together it doesn't.

I thought that once when the horn is all assembled it should be the wiring between A and C which makes the circuit and activates the horn?

[Paul Wiginton]

Slide off the collar marked A, then remove the circlip marked C. There are 2 halves of a nylon ring around the column under the collar. In one of them is a spring that holds a contact bullet against the collar. Im betting this is clogged up with dirt or corrosion and the contact is not contacting.You can pull the halves of the nylon ring out along with the wire that goes through the column and clean it up.

Paul

[dklawson]

Thank you for posting the picture. Since my wheel is also aftermarket I don't know how much of its horn wiring is original but I understand enough about it to comment. I don't think we're talking at cross-purposes.

In your picture, the wire that appears brown/black would have been purple/black in its youth. Heat and age will have discolored it. That wire is the earth connection for the horn. If you make an earth connection to it or anything touching it (such as the slip ring labeled "A"), the horn should honk. Connecting A to B should make the horn work (as you observed) because you are providing an earth path to the slip ring through the steering column. However, connecting A to C should NOT make the horn work. Point A and point C should already be connected to each other via a wire inside the steering column. Try connecting point C to point B... that should make the horn work if the internal wire is intact.

If connecting B and C does not make the horn work it is likely that the wire inside the steering column connecting A and C has failed. I have not personally had to remove the slip ring or replace that wire going from it to A so I cannot comment on what is involved. EDIT: It looks like while I was typing Paul has posted what is involved in fixing this.

With your aftermarket horn button, one side of its switch should be connected to the steering wheel or its hub and all of these have to make a good electrical contact with the steering column. There should be a second terminal on the horn button (often in the center) that makes a good electrical contact with point C... the spring loaded contact.

In summary, your current path is: power into the horn on the purple wire, out of the horn on the purple/black, to the fixed contact on the steering column (point A). From point A the current passes through the slip ring to a wire inside the steering column emerging at point C. When you push your horn button, the contact closure connects points C and B using the wheel and hub as part of the circuit.

[beardylondon]

thanks, I'll take a look.

and i forgot to mention connecting point B and C doesnt make the horn work.

Thank you for posting the picture. Since my wheel is also aftermarket I don't know how much of its horn wiring is original but I understand enough about it to comment. I don't think we're talking at cross-purposes.

In your picture, the wire that appears brown/black would have been purple/black in its youth. Heat and age will have discolored it. That wire is the earth connection for the horn. If you make an earth connection to it or anything touching it (such as the slip ring labeled "A"), the horn should honk. Connecting A to B should make the horn work (as you observed) because you are providing an earth path to the slip ring through the steering column. However, connecting A to C should NOT make the horn work. Point A and point C should already be connected to each other via a wire inside the steering column. Try connecting point C to point B... that should make the horn work if the internal wire is intact.

If connecting B and C does not make the horn work it is likely that the wire inside the steering column connecting A and C has failed. I have not personally had to remove the slip ring or replace that wire going from it to A so I cannot comment on what is involved. EDIT: It looks like while I was typing Paul has posted what is involved in fixing this.

With your aftermarket horn button, one side of its switch should be connected to the steering wheel or its hub and all of these have to make a good electrical contact with the steering column. There should be a second terminal on the horn button (often in the center) that makes a good electrical contact with point C... the spring loaded contact.

In summary, your current path is: power into the horn on the purple wire, out of the horn on the purple/black, to the fixed contact on the steering column (point A). From point A the current passes through the slip ring to a wire inside the steering column emerging at point C. When you push your horn button, the contact closure connects points C and B using the wheel and hub as part of the circuit.

[dklawson]

If B to C doesn't work, follow Paul's advice on taking the slip ring off and cleaning/checking everything. Please post back with your findings.

[beardylondon]

many thanks, will do, could be a while, but I will report back.

If B to C doesn't work, follow Paul's advice on taking the slip ring off and cleaning/checking everything. Please post back with your findings.

[mk1leg]

Strip it down and take pictures as you go and give it a good clean and use sandpaper to clean terminals and then reassemble................

[beardylondon]

hi guys,

I did what you suggested and took it all apart, it was all pretty clean, but it does now work, so I think it was the contact bullet connection under the collar, I think it was sticking, now released it seems to all work fine.

many thanks for all your help.

Slide off the collar marked A, then remove the circlip marked C. There are 2 halves of a nylon ring around the column under the collar. In one of them is a spring that holds a contact bullet against the collar. Im betting this is clogged up with dirt or corrosion and the contact is not contacting.You can pull the halves of the nylon ring out along with the wire that goes through the column and clean it up.

Paul

[Paul Wiginton]

Ive had this problem on all 3 of my MK1s, its always the same