The horn push failed many months ago, so I rigged a push button on the ski slope to sound the horn. It works, but finding the switch really fast isn't all that easy, while pushing on the steering wheel is instinctive. So, I set about trying to fix it.

Took the steering wheel insert off today. I see that in the center of the steering column there is a copper tab, and when the insert is pushed the copper tab contacts the electrical connection in the center of the steering shaft, which closes the circuit to activate the horn.

What isn't obvious to me is how the circuit is closed. Since there is (that I can see) no electrical connection between the steering wheel insert and any other part of the steering wheel assembly, how does this system work?

Pic below.

Thanks,
John
1987 XJ-S V12
75000 miles

 

The horn push contacts the metal inner on that large white plastic nut in the centre of the column. If you take a wire and ground that metal inner of the nut the horn will sound. If your horn-push copper piece is not bent outwards enough from the horn push pad towards that centre metal piece of the plastic nut, then pushing the pad wil not make the horn sound. Try bending it outwards a bit so it makes better contact.

 

It may be that the contact further down the steering column is not right. You should find a wiper contact protrudes through the outer column to make contact with the other end of the brass rod that you have at the top in the centre of the white plastic nut.

 

OK, thank you guys for that. I think I've seen the contact on the steering wheel column when I was down there for some other reasons, so I'll check it out.

But what I don't understand is this. I take it that when the metal tab contacts the metal inner on the white nut that completes the circuit to the horn relay. From what I can see, there is no electrical connection to the metal tab, so how does the metal tab contacting the metal in the white nut send power to the relay?

I don't doubt what you are saying, but I just don't see, since there is no electrical connection to the metal tab, how that completes the circuit.

Thanks,

John

 

If you unscrew the plastic nut and withdraw it, you will find a nylon insulator on the end of a long brass rod. The other end of the rod, below the insulator, touches an insulated contact in the centre of the steering column tube. I seem to remember it is sprung against it when the white nut is done up. Thus the volts are transmitted from the wiper on the column bottom to the contact in the column tube, then to the brass rod and to the horn pad contact. When you press the horn, this completes the circuit by grounding it to the permanently grounded column outer.

 

As Greg says, horn push grounds permanently powered horn circuit, pic is from '89 guide but same basics have always been the same.

 

OK, so the problem here is that there is no piece extending beyond the insulator (see pic).

I can probably come up with an easy fix for that, but wondering how long the piece must extend past the insulator?

Thanks,

John

 

That looks Ok to me. There should be a brass slightly cup-shaped end in the nylon
https://www.ebay.co.uk/itm/226414202...Bk9SR-76ytPfZA

Maybe it just needs a clean up that end?

 

OK, mine does not have any sort of electrical connection on the nylon end..no cup-shaped brass piece. So, off to the hardware store today to find a brass rod that will fit in the hole in the brass tube and I'll fashion an end out of it to resemble the brass cup. Maybe that will do it.

Thanks,
John

 

OK, now I understand. The two "seats" that the screws that attach the steering wheel to the steering wheel "insert" (the part that faces the driver, I don't know what its actually called) have an electrical connection to the splined connection. So when the horn push is pushed, the tab inside the steering wheel insert contacts the tube mounted inside the white nut, completing the circuit. I didn't realize that there was a connection between those screw seats and the tab.

Thanks all!

John

 

OK, well, not really getting anywhere...more confusion.

I did find the two contacts on the steering wheel column. The one closest to the steering wheel is grounded. The one furthest from the steering wheel has +12 volts on it.

When I insert the tube with the white nut and meter it out, its not grounded nor does it have 12 volts on it. So, I took a brass rod that fits thru the tube attached to the nut. When the white nut assembly isn't screwed into the steering wheel, I can send the rod completely thru it. But when I screw the white nut assembly into the steering wheel, I can only insert the rod 6"/150mm. If I take the white nut assembly back out, I can insert the rod (it's 12 inches long) into the steering column all the way. I don't have an inspection camera, so I've no idea what is in there that is stopping the rod from going further. I also metered out the rod when its inserted into the white nut assembly, no continuity with ground, and no voltage on it.

Can someone sketch out what is going on six inches into the hole in the steering column. Pics below.

Thanks,

John

 

OK, here's how it works.

The outside of the steering column has two holes in it. Sorry for the poor pics but they are not the easiest thing to take a photo of.



On the outside of the column are two copper contacts that protrude thru these holes and contact the inside of the steering wheel shaft. They are not exactly identical in appearance but look similar. One is connected to ground, the other to the battery bus.




Here is the inside shaft of the steering column. The metal rod that the test lead is connected to can be seen by scrolling up to the earlier photos.



When the horn push is pushed, the copper tab inside the steering wheel makes contact with the brass tube/white nut assembly. This completes the circuit since (while its not obvious, or at least it wasn't obvious to me, the copper tab inside the steering wheel is connected to ground via the two screws that hold the horn push to the steering wheel assembly.

Thanks,

John
1987 XJ-S V12
75,000 miles

 

This is correct. The horn relay coil will be receiving 12 volts so l would expect 12 volts on the relay side of the horn switch contacts.

 

https://warrjon.blogspot.com/p/xjs-s...mn-repair.html