I just read on here a small wire / plastic clip on top of the alternator could be loose and cause the light to alarm.Check the connection.
Its the plastic clip. Mine used to flash all the time and I finally had someone wiggle it around while I was looking at the gauges it that was the problem.
I personally cut off the clip and Soldered the wire to the prong and I have never seen the light come on since. The only draw back to doing that is if you need a new alternator you will have to cut the wire to get it off but I crimped a longer piece of wire to the factory one. Just my .02