Abstract: An electrical speed control system for selectively connecting an accessory to a vehicle engine having a conventional alternator driven thereby, utilizes the voltage output of the alternator stator to determine the rotational speed of the engine, and permits the accessory to be connected to the engine when the shaft speed is at or below a maximum safe engagement speed, and disconnects the accessory when the speed is above a maximum safe speed for the accessory. The speed control system further prevents reengagement of the accessory after reaching and falling below the high-speed disengage point until the rotational speed of the engine has fallen below the maximum safe engagement speed level.