Method of controlling a motor vehicle windscreen wiper motor, powered and controlled by pulse width modulation (PWM) with duty ratio (T) of determined value, in which the instantaneous fundamental period of the modulated pulses is switched successively between at least two discrete period values (T1, T2), the duty ratio (T) of the pulses (PWM) being substantially established at a determined value for at least one determined duration (Tc) of switching of the modulated pulses. Application to the reduction of the EMC noise level in the radio frequency bands to be protected.