What Are the Symptoms of a Bad Alternator, ...will the car run off the battery Options

[7TPorsh]

The other morning my car wouldn't crank; lights on dash but no juice. So I charge the battery up and start the car....drive around for a bit. Stop and start after half hour. OK

rive some more and get home...turn the car off and same thing; no juice. I take the battery to FLAPS who analyzes it and says it's bad....even though my meter says 12.5 volts.

I get a new battery and installl. Car starts and runs and I drive back to FLAPS to test system in the car. Master guru technician says machine says I need a new voltage regulator. Of course they don't car it so I drive back home.

i get in the DD and hunt down a new voltage regulator and put it in. Car start and drives...so i drive back to FLAPS. On the short drive there the car is running "on and off".

i make it there. the 2nd master guru technician hooks up the meter and I manage to barely get the car started and running but it shuts off. He tells me the same thing again, the voltage regulator is bad.

I say i changed the voltage regulator and he says no its the one in the alternator. (IMG:style_emoticons/default/blink.gif)

So I coast the car back towards home but couldn;t get it started...going to try again later.
\
So does this sound like a bad alternator? Car cranks but wont fire. Always thought it would run off the battery if alt is bad. Please help.