Geared motor for a motor-vehicle wiping system comprising: - an electric motor including: - a rotor including magnetic elements, - a stator having the electromagnetic excitation windings of the rotor, - a rotary shaft rigidly connected to the rotor, - a reduction gear linking the rotary shaft and an output shaft of the geared motor, - a casing forming a protective envelope for said reduction gear, or the electric motor, and in which said reduction gear includes a worm screw and worm wheel gear, the worm screw being rigidly connected to the rotary shaft of the rotor, the worm wheel being rigidly connected to an output shaft of the geared motor, - bearing means (23, 24) for guiding the rotary shaft of the rotor in rotation in relation to the casing, a determination device for determining the angular position of the rotor including a multi-pole magnet that is rigidly connected to the rotary shaft of the rotor, [characterized in that] and in which the geared motor includes a heat sink attached to the multi-pole magnet and made of a different material from the multi-pole magnet, in the form of an element projecting radially from the rotary shaft and laterally from the multi-pole magnet towards said worm screw, that is distinct from the bearing means (23, 24) and the multi-pole magnet, said heat sink being in an intermediate position between said multi-pole magnet and the worm screw, arranged in the vicinity of the worm screw on said rotary shaft, including an internal bush for assembly of the rotary shaft, said element being designed to form a heat-exchange surface with the internal atmosphere of the casing, the distance Δ separating said heat sink from the worm wheel being equal to or less than the distance separating said multi-pole magnet from the worm wheel. - an electric motor including: - a rotor including magnetic elements, - a stator having the electromagnetic excitation windings of the rotor, - a rotary shaft rigidly connected to the rotor, - a rotor including magnetic elements, - a stator having the electromagnetic excitation windings of the rotor, - a rotary shaft rigidly connected to the rotor, - a reduction gear linking the rotary shaft and an output shaft of the geared motor, - a casing forming a protective envelope for said reduction gear, or the electric motor, and in which said reduction gear includes a worm screw and worm wheel gear, the worm screw being rigidly connected to the rotary shaft of the rotor, the worm wheel being rigidly connected to an output shaft of the geared motor, - bearing means (23, 24) for guiding the rotary shaft of the rotor in rotation in relation to the casing, a determination device for determining the angular position of the rotor including a multi-pole magnet that is rigidly connected to the rotary shaft of the rotor, [characterized in that] and in which the geared motor includes a heat sink attached to the multi-pole magnet and made of a different material from the multi-pole magnet, in the form of an element projecting radially from the rotary shaft and laterally from the multi-pole magnet towards said worm screw, that is distinct from the bearing means (23, 24) and the multi-pole magnet, said heat sink being in an intermediate position between said multi-pole magnet and the worm screw, arranged in the vicinity of the worm screw on said rotary shaft, including an internal bush for assembly of the rotary shaft, said element being designed to form a heat-exchange surface with the internal atmosphere of the casing, the distance Δ separating said heat sink from the worm wheel being equal to or less than the distance separating said multi-pole magnet from the worm wheel.