| Generally, if they determine that what broke on your car is a direct result of an aftermarket part you install, then yes, they can void the entire waranty...
I would get a private mechanic to install your alt and battery, at least then you know it was done by a professional.
~Andrew
__________________ 2000 Sunfire GT (Black)<br />Premier DEH-P650<br />Premier TS-C504 5 1/4 components up front<br />JL Audio TR690 6x9's in the rear<br />Planet Audio P10DVC 10" DVC (x2)<br />Tsunami DB1100D (subs)<br />Tsunami DB4400D (components)<br />Knu Koncepts wiring throughout |