In that i'm not nearly as smart as I once thought, and that I have never really figured out car charging systems, I appeal for advice before I go digging into this one.

Half way to the in-law's last evening the alternator light came on. Peculiarly, the instruments (fuel, oil temp, water temp, tach) also began reading extremely low...e.g. fuel gauge went from full to almost empty.
No turn signals either.

So I dropped off my wife and immediately went home, hoping to beat darkness and the need for lights assuming I was running a total loss system. Guess I went about 18 miles with the alternator light on. And i made it. When I got home, engine still running, I measured the voltage at the battery teerminal. About 13.85.

I assume my old Bosch 35 amp (or it is 35Watt?) alternator finally outlived itself. But that instrument light thing has me puzzled. I know these things have voltage stabilizers for the instruments. Could it be there's a reference voltage directly from the alternator? How can I test the alternator? Voltage regulator?
If it's a bad alternator and I replace it with a Bosch 55 amp unit with an internal regulator, what re-wiring is required?

Hope someone out there can help me out with this. And i hope the solution is as simple as a new alternator.