As above -what happens when you switch on the side lights? But the likely reason is that the lamp holder is not earthed to the body - so check that out!
you need a good earth so if the aperture was rusty sand it back so there is good electrical contact, or run a wire from the lamp body to a sound chassis earth and paint round the lamp aperture in the wing to prevent rust.
The problem can also lie in the connection between the cap of the bulb and the lampholder, i.e. the earthing of the bulb itself. The live side gets a nice big spring-loaded brass contact, easy to see and clean, but the earth gets only a couple of tiny bayonet pins in a crudely-made, corroded lampholder, where the bit that the bayonet pins bears on is very difficult to get any implement or abrasive onto.
Check this by baring half an inch of a length of flex, and shoving it between the bulb and holder. The bulb may well then start working, showing this is where the fault lies. If it still doesn't, touch the other end of this bit of flex on a known-good earth, like the battery terminal. If it then works, the fault's likely to be the earthing of the lamp base.
Thanks for all those tips. My money is on the earthing.
It was all working fine, then another motorist behind me in a queue warned me of my intermittant brake light - that's when I found the indicator fault.
Now found an oil leak down the axle onto a rear break, so I've that to work on as well !
You wonderful people, that's the indicator working again.
The small clips that the retaining screws on the car body go into were very claggy with road grime. A bit of WD40 and a polish with sand paper was all it took.
