[jmatta]

My '02 S with 19k miles had an issue recently. I'd just removed the car from winter storage, where it was on a maintainer all winter. Had to take the car for emissions testing, so picked a nice 70 degree spring day and went out for a drive to the station, which was about 20 miles away. Car performed flawlessly, but the battery light came on shortly after I left the station and remained on for the entire 20 mile drive home.

Upon testing with my DMM, the output was only 11.8 volts at the battery terminals whether the car was running or not...obviously an alternator issue. After researching here and a couple other sites, it appeared to be a common problem and likely a bad voltage regulator. There is no Porsche part I could find, but Audi, VW and MB use the same component, so I ordered a replacement Bosch F 00M 145 350 unit (made for a German company in Mexico, for a car built in Finland).

Long story short, following 101 Projects for Boxster book, I removed the alternator (royal PITA) and installed the replacement regulator. Fired it up and voltage at the terminals back to 13.8 to 14.3...success!

This part only cost me $54 and is readily available. Before shelling out for a new or rebuilt alternator, you may want to check into this remedy, as it saved me a few bucks.