Unfortunately, these alternators aren't like the 240/740/940 alternators. They do die. I've learned (the hard way) that if it is "overcharging" it's the voltage regulator (which is a pricey little ^&$#%), if it is undercharging it is the ignition switch or the alternator. Start the car, eeeek the key counter-clockwise just a smidge, if the lights on the dash go out and look normal, viola, problem is the ignition switch, if the lights stay on, it is a less happy viola, problem is the alternator.

Hope this helps,

Chris