Intermittent electrical cut out

On my 73 lotus Europa special, every now and then my indicators stop working and also the fan. Then without doing anything they will simply work again. This also used to include the electric windows but not any more as they work 100%. I've tried fumbling about with various wires to see if I can detect a dodgy connection but no luck. I've dismantled the ignition switch and given it a thorough refresh. All other electronics on the car work fine. I'm pulling my hair out trying to figure it out.