The invention relates to a method for assembling a regulation valve (10) intended for controlling the flow of gas in a circuit of a motor vehicle equipped with a heat engine, said valve (10) comprising a magnetic structure (15), a rotation axis (21) and a toothed section (16). The main feature of an assembly method according to the invention is that it comprises the following steps: - mounting of the toothed section (16) on the rotation axis (21), - rigid connection by welding the magnetic structure (15) to the toothed section (16) fixed to the rotation axis (21).