The electrical supply cable for the motorized fan unit of a fan assisted heat exchanger, for example the cooling radiator for a motor vehicle internal combustion engine in which the radiator comprises a matrix consisting of tubes with cooling fins, extends through the matrix via a bore through the latter in which the cable is guided by an insulating member disposed within the matrix. The cable therefore does not pass along the face of the matrix on which the motorized fan unit is attached, so that damage to the cable is avoided.The cable may be replaced by conductive elements which are encapsulated in the insulating member itself, these conductive elements cooperating with contacts of the motorized fan unit and of an external connector.