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Horn Wiring

Posted: Fri Apr 05, 2019 11:47 am
by Graham
I have stupidly caused a dead short in my horn button (don't ask!) resulting in smoke and some obvious burning of insulation. Thankfully this was only slight although I did reach for the extinguisher.
My problem is withdrawing the control tube (48) so that I can get to the wiring. At the steering box I have removed the clamp (53) from the end cover (27) and re-clamped it at the end of the tube - rather like you replace a nut so as not to damage the thread. However I still can not get the tube to slide up. I can rotate the control tube (using the clamp) but I notice the inner column (12) also rotates.
My theory is that the various grommets (52) and bushes (50) are stuck to the control tube but my fear is that there is something I have missed and I don't want to cause damage.
I'd very much appreciate advice before my ignorance is joined by brute force!


Re: Horn Wiring

Posted: Fri Apr 05, 2019 1:14 pm
by luli
WD40 - push and pull - patience. Remove first the bottom plate of the steering box to decrease friction and improve pushing.

Re: Horn Wiring

Posted: Fri Apr 05, 2019 8:29 pm
by TonyG

I’m not familiar with post war cars but with the pre war models I’m pretty sure that access to the top of the advance control tube and the wires is possible once the horn etc is disconnected. Assuming the post war cars are similar it should be possible to replace the wires with the tube in situ. I did this by first passing a stiff thin wire through, attached to the new wires and taped to avoid snagging. It is a fiddle to get all the wires through as some are quite thick due to the current going to the lights. Using relays can help here so that lower current cable can be used.
The tube should rotate easily in the centre of the column so it can remain in the same position while the steering moves. If the tube is moving with the column, as you mention, then this will impact on the cables within; specifically at the bottom where they exit the column as repeated twisting may cause faults. With this in mind and assuming I’ve understood correctly, I’d suggest leaving the tube in the column but ensuring it rotates freely and then replacing the wires as described above rather than risk damage to any seals taking the tube out.
My apologies if your car is completely different to mine and this response makes little sense! It will be good to hear from you how things progress though.


Re: Horn Wiring

Posted: Fri Apr 19, 2019 7:09 am
by Phil - Nottingham
Replacing the wiring is a good idea anyway and also using PVC. The newer thin wall cables are stiffer and thinner and will also carry a heavier current. Nevertheless, I would still fit relays for the horn and the main and dip beam as well as fusing. I have heard this cable which is used in all modern cars degrades over time of 15-20 years but heat has an effect as it does with any plastic or rubber/nitrile. I would not expect it to last 80 odd years some Rover owners expect the OEM cables have!

Being stiffer and a lot thinner there should be no problem sliding new stuff in situ. The problem will be getting the old cables out if the too have stuck inside.

If you are bothered about originality over practicality and safety the new cables where showing can be disguised and the relays/fuses easily hidden.

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Re: Horn Wiring

Posted: Fri May 31, 2019 11:10 am
by Graham
Job done. Thanks for the advice.

After some effort and without disconnecting any wiring I managed to ease the control tube upwards sufficiently to examine the underside of the horn mechanism. I was terrified of breaking the bakelite but by concentrating on the bottom of the tube everything was fine..

With some relief I discovered it was not the wiring that had shorted but that the rubber washers which electrically isolate the contact plate had failed and the connecting strip had come adrift. After some rummaging in some 'you never know when this will come in useful' tins I found just what I needed, the mechanism was rebuilt, the strip reattached and all is well again. Thankfully there had been no damage to the horns themselves so that glorious get out of the way noise is back.