the volute 1 a concave inner face 103 at one end of which is situated a housing 102 for the connector and at the other end of which is arranged the cooling element 104 featuring at least one cooling wall 105 and additional fins 106 as the case may be in the example represented this wall 105 is situated at the end of the module 9 and runs along the face 71 of the aperture 7 in mounting position of the module when the connector 160 has been clipped fully into the complementary connector of the motor m the half casing 100 also features spacers 120 allowing for the mounting of a printed circuit 170 represented diagrammatically in fig2 d this circuit 170 features electrical power supply contacts 175 and various electrical components self inductive components for example an input choke l 0 capacitive components c 5 c 7 c 9 etc as well as transistors t 1 t 2 t 3 and or a thyristor thr so as to avoid over rapid thermal propagation from one element to the other the casing advantageously includes at least two compartments 111 and 112 separated by one or more partitions 110 which particularly makes it possible as represented to isolate the input choke l 0 arranged for this purpose in the compartment 111 which is juxtaposed with the exchanger 104 and which is separated by the partition 110 from the compartment 112 which carries.