Yeah I got a 98 LX (I-4) sedan and mine's starting to do the same thing. Like they said, it's the alternator most likely. Been there, done that before on my other cars. Mines got the stock battery and alterantor with about 70k miles on it. What's probably killing it is the amp sucking up all the power to power the system. Usually it's good and won't whine, but if I get the AC going and say the rear Def. is on, sound is cranking, lights on, etc. then you hear that baby.