After 25 years,the offside trafficator still works but fouls the rear door as the plastic has distorted slightly and the clearances are very tight.
One spare I have has a similar shape but is a later type (Lucas SF37). These specially shaped semaphores have a bulge where the festoon bulb fits and appear to be very rare (none seen on eBay in the last two years)
I found that the auxiliary fuse blew if I operated the horn at the same time as the right trafficator.
It was a clear indication that the four-way cable to the horn button and trafficator switch was perished.
The assembly pulled out very easily once the bottom clamp bolt (at the end of the steering box) was loosened. Don't forget to have a bowl underneath to catch all the oil out of the steering box - and to refill it afterwards!
As putting the assembly back can be difficult, I found it easy (though mucky) to remove the end plate off the steering box (two screws) - later models are different.
I then had the end plate (complete with a felt seal, not shown in my parts book) and a thin steel plate to clean up. The gasket remained on the box so was left in place.
Clean and dismantle the horn end of the assembly carefully and mark where the four the wires go to. Rewiring was fairly straightforward - do it methodically and nothing will go wrong!
I used 17 amp cable for the supply feed and horn wires and 8 amp cable for the left & right indicators - these four wires just fitted down the inside of the steel tube.
Having noted the colours of your new wires, reassemble in reverse order as they say.
As I had taken the end off the box, the wires slid easily down the steering tube and I then slid the steel shim followed by the felt seal and end plate back over the wires, finally tightening the end plate clamp to hold the tube in the desired position.
All that is left is to reconnect the wires to the terminal block next to the coil and watch the trafficators bounce up and down!
On my terminal block - from the left: black= Horn; green=Right Indicator; red=Fused supply (from auxiliary fusebox outside the cutout/regulator); blue=Left Indicator
The nearside trafficator was well beyond repair and as no spares had come up on eBay or other vintage suppliers, the only option was flashers (no!) or a later trafficator.
Later SF80 trafficator arms are more robust (but therefore wider) so the slot in the central pillar was widened to suit the later model.
The mountings (held by a 3/16" BSF bolt!) also had to be modified and I altered the backplate of the SF80 trafficator plus spacers to get the position just right.
although the offside SF27A trafficator worked and was of the right shape, it was not the original one with the car as the mountings had been modified.