Just had the same problem on my 1972 S3. In my case it turned out to be the bulb holder - the sprung connector wasn't engaging properly with the contact at the base of the bulb. New holder fitted and problem all solved.Grateful for any advice on a battery charging problem on a 1972 series 3. The ignition warning light doesn’t illuminate but I’ve got power at the bulb holder and at the alternator brown yellow wire coming from the warning light. I’ve checked different bulbs that are known to be working, could it be an issue with the bulb holder?