I've had water, coolant, power steering fluid thrown over the alternator (original @ 205K) and it is still going. The only time I ever had the alternator warning pop up was when the serpentine belt was slipping. Although you'll like notice the steering get stiff - when mine happened, it was when I'd turn the wheel far enough to the right or left to put load on the PS pump. The steering got stiff because the pump couldn't run fast enough due to the slipping belt, which also caused the alternator to not spin fast enough to trigger the dash alert. It worried me at first as well until I realized what was happening. Replaced the belt and no issue since. Just food for thought if the alternator tests out good.
2004 M6 GTO
* 2x Cartek Cam | Kooks SS Headers & Hi-flow Cats | LM1 Intake | Billet Performance Catch Can
* Whiteline Sway Bars, poly bushings | Pedder's End Links, Diff Insert, Drag Springs | Lovells Front Stock Height Springs | KYB shocks
* 18x8 & 18x9 ROH Drift R | SAP front grille & spoiler