I've just solved an electrical problem that is unlikely enough to be worth sharing. For a couple of days the engine of my 1989 240 has sometimes run on slightly at switch off, then shuddering to a stop with clicking sounds from a relay somewhere and horrendous audible noises from the radio. The bulb failure warning lamp was also acting up, but that's not unusual. After a few occurrences I realised that it happened when I still had the footbrake applied when switching off the key. The fault ? There was an internal short in one of the stop/tail lamp bulbs. The (non-ignition) stop lamp circuit was feeding back to the ignition controlled "day running" light circuit, and then presumably to the ignition circuits etc. I've also been driving around with the brake lights on but no-one told me this !
