A fan-motor unit comprises a fan driven by an electric motor, both mounted on a support, at least one inlet (I) and one outlet (S) for a forced air flow, an electronic circuit board for controlling the motor, and a radiator at least partially immersed in the forced air flow. The radiator has a curved peripheral edge determining a convex face and a concave face of the said radiator, the electronic circuit board being in contact with the said radiator on the concave face side and a substantially cylindrical bearing surface on the convex face side of the said radiator. A radial gasket that forms a skirt comprises a first end secured to the support, a free second end, and a substantially cylindrical interior face between the first and second ends, and the interior face of the radial gasket bears against the bearing surface so as to isolate the electronic circuit board from the air flow.