2000 Malibu alternator problem

Since I've owned this car at 45,000 km(28K miles) the alternator will sometimes give a reduced output indicated by dimming headlights and dash lights, etc. This usually happens after you start it and the car is first being driven and you come to a stop sign and the RPM's go a little lower (below approx. less than 1000 RPM). It will do this a couple of times and then be good until the next time I start it about an hour later and so on.

I took it to the dealership at about 50k and they said the alternator was good and gave me a bulletin from GM stating "slow ramp up times" for these alternators. I decided to live with it and now I'm at 105K and it appears to be getting worse and more frequent.

Do I just get another alternator and be done with it or is there some other cause that I may be overlooking. I don't want to throw money away needlessly.

Thanks

This has never happend to my 98 Malibu. You can take the alternator to a repair shop/NAPA etc and they will load test it. I just witnessed NAPA testing mine here in Canada, it was quite an extensive test, it passed, and they did not charge me.