I had similar issues to this Ruairidh.
I’d indicate and as I turned the steering wheel the horn would sound, the indicator switch was shorting between the switch and the metal on the steering wheel.
What I found was on the central unit that slides down inside the steering column and houses the horn button, there is a recess where the indicator switch sits.
I did try some shrink tubing to cover switch area that was shorting but this caused the switch to stick and so removed it.
There may be a more technical way of correcting this, but I simply took a very fine mini file and dressed the recess and the area that the switch was making contact and once clear the problem disappeared.
07-06-2021, 09:52 AM (This post was last modified: 07-06-2021, 10:12 AM by A G Wood.
Edit Reason: Added text
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I don't know if the detail arrangements are the same on Sevens, Ruairidh but I had a similar issue on my Fourteen and I discovered the soldered horn wire terminal tab at the switch was intermittently touching the trafficator cancelling mechanism (only when the trafficator was activated) inside the steering wheel center. On more careful looking it appeared there was an extended piece of vulcanised cardboard (long gone) under the terminal that was supposed to stop that happening. I carefully bent the terminal to give it a bit more clearance, but plan to do a more 'professional' fix one day...
Edit: pic added, it actually is blurry it's not your eyesight going
A picture always helps, so I attach a link to a picture of my steering wheel and indicator switch as it is now.
My memory failed me in that I said I had removed the heat shrink cover over the indicator switch, as you can see it is still there!!
I found that when I put the indicator switch on in either direction it came into contact with the recess in the central Bakelite(?) column housing the horn push. In doing so it moved the indicator switch closer to the steering wheel and actually came into contact with the steering wheel when the steering wheel was turned. It would spark when tried out in the garage.
I firstly went for the heat shrink coating in an attempt to isolate the indicator switch from the steering wheel. You can actually see that the coating of the wheel has been ground off in the area of the indicator switch. Unfortunately this then caused the switch to jam.
I then increased the depth of the recess in the Bakelite(?) central column using needle files and also removed an area on the steering column so that the indicator switch could operate without any contact with either steering wheel or the central column, and as can be seen the heat shrink is still in place.
I have had no further issues with horn going off when the indicator is on or when turning the steering wheel.
Think the steering wheel was probably recoated by your father a long time ago, it was one of the first parts I had repaired by a specialist, sadly don’t have the paperwork to confirm.
