This heating assembly comprises a thermally conductive tube (42), to be immersed in a thermally expandable material of a thermostatic element of a valve, an electric heating resistor disposed inside the tube and from which there extend electrically conductive wires (62), and a unitary housing (1) made from plastic, through which the fluid to be regulated flows via the valve, and which is secured by over-molding of a longitudinal end portion (44) of the tube. In order to make the molding of the over-molded housing simple and inexpensive to carry out, while being easy to adapt to various geometric forms of the heating assembly, the invention proposes that, before the housing is molded, a reinforcement (7) for supporting the wires outside the tube, which is separate from the housing, and to which the housing is secured by over-molding, can be securely mounted on the end portion of the tube and supports the wires outside the tube, said wires being externally mounted on the reinforcement, and, when the housing is being molded, keeps the wires in place while the plastic material of the housing coats these wires, the reinforcement and the end portion of the tube.