Last night, while I was sitting in the car and the engine was idling, the battery warning light came on. "Oh", thinks I, "the fan belts's gone or the brushes have worn out." Leeked under the bonnet and found the alternator belt was fine (it was dark and there's a not of stuff in the way but I think it shares the cambelt.)
Revving the engine made the light brighten, a lot, almost to the point of popping the bulb. If you remember the scene from the film "Poltergeist", where the lights in the house brighten almost to he point of pain, that's what it was like.
Since I was about 20 miles from home, I decided to nurse the car home and sort it out this morning. While driving along the motorway, suddenly the dashlights and the headlights brightened perceptibly and the engine management and ABS warning lamps came on (engine management steady, ABS flashing on and off.)
This spooked me a bit, but I was on a motorway and didn't want to stop. Some minutes later, all the warning lamps, including the battery light, abruptly went out and the car returned to normal. It seems fine this morning.
So what do I need? An exorcism, or something more mundane?