It was a little different though. When I shut the engine off the alternator light was off when its usually on. When I took the key out it came on. This happened at the first fuel stop of a weeks camping vacation (had to do more hiking than driving.) It turned out to be a shorted diode in the rectifier. It was a Bosch alternator out of a Peugeot diesel that, it turns out, thanks to a local car electric shop, to be the same as a Porsche and cost $30