Abstract: The operating speed of a motor vehicle alternator is controlled based on the frequency of power generated by the alternator. Since the frequency of the alternator power is representative of engine speed, the alternator is shifted between a high speed gear train for low engine speeds and a low speed gear train for high engine speeds. When shifting to the high speed gear train, it is only partially engaged for a brief initial time period to more gradually accelerate the alternator armature toward the corresponding high operating speed. Preferably, initial clutch pull-in is sensed to start the partial engagement period of the high speed gear train. The load on the alternator drive during shifts to high speed operation is further reduced by turning the alternator field current off prior to partially engaging the high speed gear train.