HORN PUSH QUESTION

[mig_man]

Hi
this may seem a stupid question but can someone please tell me how the horn push is meant to work.

My bus is a '72 crossover model. I've been restoring it for the last 4 years and now that I'm getting closer to the end I'm struggling to work out how all the bits go that weren't bolted on when I bought it in a part-dismantled state.

It's a standard steering wheel but the centre button was missing. Looking into the wheel there is a metal ring with a connector lug for a spade terminal. I recently bought a new plastic 'push' from VW Heritage. This push has a metal sprung clip round the outside and it is a very tight fit in the metal ring. I've removed the 3 screws securing the metal ring and there seems to be remains the some sort of insulating ring underneath it. Before removing the metal ring it was tight in the wheel and making good electrical contact with the splined centre. Since removing the ring there is now slight movement of the ring on the mounting screws.

My assumption of the way that it must work is that the horn earth wire must come up through the centre of the steering column shaft and connect to the terminal on the metal ring. The ring must be meant to have a large diameter spring underneath it (insulated) which pushes the ring away from the splined boss, thus breaking the electrical contact with the wheel. When the plastic 'push' is pressed it moves the metal ring (compressing the spring) and the metal ring touches on the contact part of the wheel thus completing the earth contact.

Am I correct or am I wrong? If I'm right then there are two things I still don't understand.
1) how the hell can the wire feed into the shaft past the flexible coupling and surely it will get caught up as the steering turns? 2) how does the column itself actually earth? My multimeter reveals that my outer column is insulated both from the body and from the inner column.

If need be I may just mount a simple push somewhere near the dash but it would be nice to have it working as it's meant to!

Many thanks
Tim

 

[gvee]

I can offer a couple of bits of advice:

1) There's not one big spring, there's three: one for each screw.
2) The wire down the steering column is bolted to one of the 4 corners of the steering coupling via an O-ring connector.

 

[starbiscuit]

Just been through this myself on my 1970 devon.
My PO was evidently unaware of the magic of electricity and had given up leaving the whole loom looking like magpies had nested in it.

Anyway, the horn.
An ignition-live feed from the fusebox runs under the floor to the horn (+ terminal).
The low-side of the horn runs to a 6mm spade (tab) on the bottom of the outer steering column, which pokes out through a plastic insulating ring that keeps the column isolated from the big round plate that bolts it all to the floor.

The low-side path from the horn then travels up the outer column and connects to the inner shaft by the top bearing, wedge ring, and big brass spring, that are held in electrical contact by pressure from the nut on the steering wheel.

The splines and lower metal parts of the steering wheel are thus connected (indirectly) to the low-side of the horn.

The horn ring (that carries the plastic horn-push button) is isolated from the rest of the steering wheel by plastic spacers, held up by 3 springs, and connected (by spade terminal) to a wire that runs down the centre of the column to one of the steering box bots on the square rubber coupler, thereby being grounded by the steering box internals.

So when you push the horn ring into the steering wheel, you are connecting the low-side of the horn to ground; current flows, noise is made.

Of course, this all relies on the whole steering column being isolated from ground, especially at the floor and at the dash mounting bracket, otherwise the horn will sound whenever ignition is on.

The problem my PO had was bizarre. He eventually ripped off the indicator switch and the wire between the horn and the steering column to stop the horn sounding all the time.
Eventually I found that his real issue was caused by the rubber steering coupling that was, in fact, conductive :shock: . The metal-lined bolt holes were electrically connected, thereby making the circuit between the steering shaft and steering box, and sounding the horn.

Having fixed that, the problem I had was that the indicator switch C-shaped clamp was too close to the ground terminal of the headlamp flasher switch, causing the horn to sound with ignition on. My fault; the clamp was a part I made because the original was missing. Fixed with a file and some insulation tape .

My tip is that if you are replacing the horn-to-steering-column-tube wire, then it is much easier to connect it to the column tube with the column removed from the floor, then pass it through the floor when reassembling the column and connect to the horn last, than to connect the wire to the horn first and then try to connect it to the tab that you can't see or feel around the steering coupler when in-place.
(Note also that the inner steering shaft can stay in-place throughout)

Hope this was useful.

 

[mig_man]

Thanks for both of your replies.

After George's reply it suddenly all made sense to me and now it's been confirmed that my understanding is correct.

It wasn't obvious to me before as
a) the spade terminal at the bottom of the outer column had broken off. I can now see where it was once riveted
b) the top bearing was incomplete or unbelievably worn and the shaft could wobble from side to side by several millimetres (which wouldn't impress me or the MOT man much!) As the bearing isn't available I turned a bush out of a length of delrin that I had lying about. I'm sure this will do the bearing job brilliantly but doesn't do anything for the electrical conductivity! This is why my inner shaft is insulated from the outer column.
c) the wedge and brass spring you refer to are missing from my column. Presumably these are to help with the electrical connection. It was the presence of the large spring on the parts diagram that made me think it must be for the horn push ring rather than the more obvious spring for each bolt.

Had I asked this question months ago before I made the delrin bush I could have incorporated a conducting ring into the design but it's a little late for that for that now. For the time being I've decided to simply add a push button by the dash to get the horn working. In reality thats probably easier than reaching for the push in the centre of the steering wheel! Not as neat or original though. I think I've got room above the bush to add a contact ring of some description but I'll leave that till a later date as I've got to crack on and try to finish the bus and there's still so much to do.

I've got to sort out/refurbish the steering wheel itself so I'll get the contact ring freed off and find some suitable springs so that the horn push will be operational ready for if/when I sort out the column/shaft connection.

One thing I've done now is to swop the horn onto the hazard switch fuse. I'm not keen on having a horn that only works when the ignition is on. If I'm parked up in a layby or car park and someone looks like they're reversing into me I want to hit my horn THEN, not fiddle about trying to turn the ignition on 1st! Both my Triumph Spitfire and Austin A35 were wired like this from new and I'm surprised the VW isn't.

Thanks again. I'm starting to wish I'd used the forum before as it might have saved me time before. I'm sure I'll need it again as there are so many bits in the boxes that I don't know what they are or where they go (or if they're even from the bus!). The joys of buying a partially stripped project instead of a complete one!

Tim