[DFWX]

While traveling on an 1100 mile trip at night in her 1984 928S (I have an '80 928), the gauge showed it discharging and it when dead within 15 minutes (dead battery).
A local shop (there) told her it was the alternator, so she stayed in a motel while one arrived the next day. However, that was not the problem or the cure.

The car charged fine on the highway the next day, until that evening when she turned on the lights - and it again began discharging - so she brought it in the next day without lights.

The car charges fine. But if ANY lights are turned on, it will show discharge (below 12 volts). If just the blinkers are turned on, the gauge needle will dip below 12v with each blink. Making it more bizarre is that turning on just the fog lights will cause it to show less than 12 volts (or discharging) also. Yet it only has to do with lighting.

This does not occur with any other electrical components (a/c, fan, stereo, wipers etc) and the car runs fine.

I dread taking it to a Porsche dealer with this puzzle.

Does anyone have any idea what would cause the electrical system to go to discharging due to any light going on?

I could REALLY use some help!!

Thanks.

Mark