This heating cartridge (1) includes a thermally conductive tube (2) to be immersed in a thermo-expandable substance of the thermostatic element, electric heating element (3), arranged inside the tube and provided with wires for conducting an electric current supplied by an external current source, and connection element between the wires and ports (7) powered by the external current source, these connection element comprising a support base (4) integral with the tube. In order to facilitate the electric connection between the wires and the ports and make it more reliable, the connection element comprise coupling pieces (6), supported by the support base and designed to pinch each port against the corresponding wire.