2.7 Liter w/ 138,000 miles - keeping her in shape

Thanks guys! I feel better now, although the car is out of service at
the moment. After three weeks of driving 50 miles a day with no
problems, the battery light came on. Shortly after that my
headlights, dashlights, and radio went out while the car was running.
At first I suspected the alternator, but I checked it on the car with
a voltmeter and it seems ok. I've been putting off testing the
battery (because this happens while the car is running), but I'm going
to give that a shot tomorrow and hope that's the issue. After reading
a few posts it sounds like a bad battery could cause some funky things
to happen while the car is running in these cars. Does anyone know if
the alternator could be giving me intermittent problems, as in it only
works part of the time? I thought when alternators went bad they died
completely.

Thanks again!
-SS