97 Saab 900 Convertible 2.3 alternator problems
 

I have a 97 Saab 900 S with the 2.3 liter engine.
My alterator went out and I had it replaced with one I bought from advanced autoparts it lasted almost 100 miles and went bad so I replaced it again and it went out again this time it lasted about 600 miles. Does anyone have an idea why the alternator keeps going out ? I have checked the cable going from the alternator to the starter it looks fine the light comes on in the instrument cluster.Yesterday when the alternator went bad I noticed that the bell kept ringing even thought the key was out of the ignition but once I started the car again and turned it off the bell stopped.