Method for slowing the icing of an air-conditioning system for a motor vehicle, and corresponding air-conditioning system

The method involves measuring (E2) temperature of external air flow and comparing the temperature with a temperature threshold. Moisture content of external air flow is measured (E4) if the temperature is lower than or equal to the threshold. Speed of external air flow is regulated according to the content. The speed of external air flow crossing external heat exchanger is reduced (E5) if the content is greater than upper moisture threshold. The speed of external air flow crossing the exchanger is increased (E6) if moisture content is lower than or equal to the upper moisture threshold. An independent claim is also included for a thermal conditioning system of car.