Intermittent Horn Feature

[ElliottN]

My horn has decided to work according to new rules. With steering wheel at 12 o'clock - hit the horn push - the silence is deafening. Turn steering wheel to anywhere between 6 & 3 o'clock or 6 & 9 o'clock - hit horn push - horn works! I suspect the problem is grounding as I recall reading the steering column is grounded by a strap somewhere and I'm guessing it needs a disassemble/clean/adjustment or replacement but where is the earth strap?

Important to note - I do not have standard steering wheel and horn push (have Momo 12" wheel with supplied boss & horn button) but I have removed the bezels over the indicator/light stalks & disassembled the push button, wheel and boss to check the wiring and cannot find any fault. Have also tested horn to ensure it has not decided to work on some part-time basis but it's fine.

If it's not the earth I guess I'll have to pull down the steering column looking for a pinched wiring problem between the boss and back of the dash.

Any suggestions?

thanx.

[steveww]

The steering column should be grounded. Check that this is true as you turn the wheel. There is an earth strap that "jumps" the UJ in the column, check that this is OK. You can check the other wiring by shorting the ring behind the steering wheel to ground, the horn should sound.

[types26/36]

Because the steering rack is mounted in rubber the rack also needs grounding, there is usually a black wire that runs from one of the rack "u bolts" to the plate that covers the rack pinion.
As your problem is intermittant it is more likley to be related to the steering coupling bridge (as mentioned ) or to the steering wheel connestion.
Brian.

[ElliottN]

Ok - first I check the steering column grounding (should be a strap over the column near the UJ at the steering box).

Note - problem is NOT intermittent. It is consistent and absolutely repeatable in that horn works in the 3-6 o'clock and 6-9 o'clock range, not elsewhere. As the 9-12 & 12-3 range is where it doesn't work and that is where most of the driving happens (i.e. around and immediately either side of straight ahead) I'm guessing the column is a tad more worn from the strap on that position on the column and it is losing the earth contact in that 180 degree radius.

If the earth is good and the rest of the wiring tests OK - it's got to be the slip ring/sprung connector between the boss and the wheel/horn button.

thanx.

[robb4100]

Sorry if I state the obvious, but it seems like you are having a mechanical break in the circuit as you turn the wheel and need to isolate whether it is from the steering column to the frame, whether it is from the ring to the battery or whether it is the horn button mechanism.

I suggest removing the horn button, and then completing the circuit from the steering column to the battery with a tester (bypassing the ring) and turn the wheel. Does the circuit break as you turn the wheel. If it does then the problem is between the column and the frame.

Likwise complete the circuit between the ring and the frame and run the tester all around the ring looking for dead spots- I cannot think of why there would be a dead spot but rule it out.

If both of those work then it must be the button and the plunger which are the only moving parts. Is it possible that the plunger does not reach the ring all the way around?

Does this make any sense?

[ElliottN]

Thanks - I followed all that through. The problem was/is steering column to ground.

I was only getting a ground when the wheel/column was moving through about 180 degrees - 3 to 6 to 9 o'clock. I removed the wheel & boss and tested the circuit from the horn to the relay to the slip ring behind the wheel boss - all OK. Then checked the push button through 360 degrees on the slip ring and it was OK.

What has thrown me is that I was expecting an earth strap somewhere on the lower section of the inner column - between the firewall and the flexible coupling - but there is absolutely nothing there. There is also nothing that I can find on the steering column inside the car and my steering column brackets are NOT grounded. At the moment I can only conclude that grounding is occuring through the flexible coupling to the rack. This seems problematic to me as despite the 4 bolts giving a good connection through the coupling and my steering unit being well grounded, it would rely on the pinion shaft/pinion/rack grounding and that is a set of well greased moving parts!

So - I cleaned the flexible coupling (without dismantling at this stage) and everything has started to behave again.

Unless I learn something else soon - my next job will be to install an earth strap between the lower end of the column and the frame. If the ground is through the coupling - the problem will strike again sooner or later.

Thanks again all.

[steveww]

As I mentioned earlier the UJ on my car has a bit of wire "jumping" over it to ensure a good path to ground. This might be a worth while mod to perform on your car.

[richardcox_lotus]

Initially I thought it might be that good-old cut-out switch, but I'm not sure how I should re-connect things if I remove the switch from the car.

I can understand how a dodgy earth connection might prevent the horn from working when I [b]do[/b] want it to, but what would [b]make[/b] it work when I [b]don't[/b] want it to ?

Car is a '72 Sprint. Off to Le Mans in it on Thursday, so you might hear me coming from a looooong way away

[deep_socket]

Elliott:

To elaborate on what has been said by others:

I believe the horn in the S4 is wired as follows (at least, the one in my 72 Sprint is):

Hot lead (purple) to horn; from horn, ground wire (purple and black) leads via harness to the steering column and thence to the horn push. From there, when the horn is pushed, the circuit is completed to ground through the steering column. The steering column is grounded via the steering box, which itself must be grounded by a separate wire.

The tricky bit is the U-joint in the steering column, just above the rack. This needs to be jumped by a short length of flexible cable--preferably flat copper braid--soldered to round eyes and bolted to the fixings on either side of the UJ. It needs to be long enough to bend when the wheel is turned, but not long enough to snag, and flexible and strong enough to hold up to repeated flexing.

Sounds like that may be where your problem is--the jumper wire may be broken inside, so that the connection is good with the wheel at 12:00, but not when it is turned. At least, that was the problem with mine!

Bob

[steve71]

Hi richardcox_lotus,

I had a similar problem in Dad's S4. The steering crash impact clamp was not stopping the columns from sliding into each other and when the steering wheel boss ended up to far down the horn would start to go off. There is thread about it if you do a search on "impact clamp" you should find it. Not sure if this is your prolem but it may help.

Bye,
Steve.

[richardcox_lotus]

Thanks for the replies guys. I guess the reason I was summising that it was the cut-out switch was the circumstances in which the fault occurred, namely:

1) Parked Car outside. Set switch in glovebox, went indoors

2) Later on, got back into car, moved switch, turn key, horn sounds ! The wheel had not been moved in position !

....further investigations revealed:

- Removed steering wheel & boss. Horn would still sound when ign key turned.

however.......

- if switch was set to allow car to start, it would indeed fire up (albeit with the horn going off).

I removed all the horn connections, cleaned them up between purple/black wire in engine bay & horns/relays/earth, and reconnected - all seemed to work as intended, until a later test turning the switch on & off, when the horn seemed to go off again.

In frustration, I bashed the (now re-connected steering wheel) boss & it stopped !

...so my other thoughts are ....Relay problem ? or
...earth strap on steering u/j - this is connected in the right place, broken internally ? or
...impact clamp. - This is pretty rock solid on my car, so I don't think I'll be able to set it any tighter than it is at the moment to prevent slip.

For expediancy sake, if I want to turn the horn off totally, will removing the earth lead from the horn itself do the trick ? Is there anything else on this circuit that will cease functioning if I do ?

rgds

Richard Cox

[john.p.clegg]

Just had a quick look at your last posting and it seems to me your glove box switch is playing up,giving 12v to both the horn and ignition.......

Go check

John