An exterior rearview mirror assembly for a vehicle includes a mounting portion mountable at a side of a vehicle, a mirror head portion adjustably mounted at the mounting portion, and a reflective element at the mirror head portion. An actuator is operable to impart pivotal movement of the mirror head portion relative to the mounting portion and about a generally vertical pivot axis to pivotally adjust the mirror head portion relative to the side of the vehicle at which the mounting portion is mounted. The actuator comprises at least two motors and the motors are operable in tandem to cooperatively rotatably drive a common gear of a gear system to pivot the mirror head portion relative to the mounting portion. Responsive to a determination of the rotational movement being below a threshold speed, a shutoff circuit deactivates at least one of the motors irrespective of current draw by the motor.