Take it out, setup a few battery's to out put 24 or 36 volts, and spike the alternator, hopefully that blows the diodes, another killer is prolonged contamination of oil or diesel, but they would see that and claim its not a waranty issue because it wasnt caused by the alternator.
well, i also think that its shady, but what could kill an alternator or electrical device: * Excessive Heat * Direct short * prolonged 100% duty cycle and excessive current draw