This happened after the car has sat out for a couple of weeks, but it was fine the last time I drove it. When I start the car the voltimiter is at 16 instead of the usual 14, and after driving for 5 minutes the dinger would go off and then the voltimiter would oscilate between 12 and 16 volts. I can also hear the alternator "whine" in and out each time the volts go up and down. Car has 205k and the altimiter was replaced at 170k. Kinda young for the alternator to die out. I swapped out another battery but the behavior remains the same.

Whats going on and how can I fix?

Take the alternator off, run to Autozone and they can bench test it for ya. You may walk out a proud new owner of a reman AC Delco alternator

There'* really no gauging for when failure can happen. Might seem early, might simply be time as the moisture and cold is creeping in on us.

Have it tested out and see if the regulator isn't on it'* way down the path.

My thoughts would be either something is coming off and on, like AC and drawing a good amount or the regulator is leaving the building. (most likely regulator)

The regualtor... where is that?

I will be taking the alternator sometime tomorrow for testing.

The regulator is internal to the alternator. When you bring the alternator in..you are testing the alternator and regulator at the same time.

I would check out your alternator first... It probably is the problem... However, my parents had a problem with the voltage spiking randomly in their 98 Chevy Venture. The mechanic replaced the alternator, then replaced the brain, then eventually (After my parents bringing it back 3-4 times) found the problem was corrosion in one of the fuse boxes.

Your absolutely certain the alternator is whining? Theres alot of things under the hood that could cause that noise, make sure its that. An alternator test at Advance or something would be great, just make sure they test it right. (had a guy connect one up wrong and told me it was fine when it really wasnt for a 86 Dodge Pickup). Make sure all your terminals are clean, and check ur fuse box. Something shorting would cause an overload protector to trip repeatedly, which would cause the voltage to oscillate back and forth like that.