A method for controlling an alternator or alternator-starter of a motor vehicle, the electric machine being capable of providing an electric current, the strength of which varies on the basis of the excitation signal (EXC). A duty cycle is associated with each excitation signal. The method includes comparing the difference between the duty cycle values of two consecutive excitation signals at a predetermined threshold. If the difference is greater than the predetermined threshold, a gradual response phase is released, during which the duty cycle of the excitation signals is gradually increased, particularly in a substantially linear manner. At the start of the gradual response phase, the duty cycle of the consecutive excitation signals is increased by a predetermined jump (D,B), then the duty cycle is gradually increased. The duty cycle jump at the start of the gradual response phase being less than or equal to the release threshold of the gradual response phase.