Before jumping on an alternator replacement:
is your battery light on all the time, or only at certain rpms?
A STEADY battery light (actually has nothing to do with the battery... it is actually a CHARGE state light) could indicate either a faulty alt (not charging at all) or a bad "megafuse" not allowing a GOOD alt to charge the battery.
a flickering light would tend to disprove the megafuse, but point to the alternator itself, or POOR wiring between the battery and alt, or ground.
Ray
