Abstract: The invention relates to a starter motor switch in which there are arranged a stationary magnetic core and a winding at the center of which a plunger moves to act on a rod, a portion of which carries a contact intended to establish contact between two terminals, of the type in which the stationary core delimits a chamber and a chamber and of the type in which the stationary core has a cavity in which a portion of the rod is accommodated, wherein it comprises a sealing partition comprising a transverse plate resting against the front face of the stationary core, which is extended by a rim which interacts in a sealed manner with the cover, and comprising a central part, the shape of which complements that of the central cavity with which it interacts in a sealed manner.