Abstract: A heat exchanger, typically an air conditioning condenser for a motor vehicle, has a fluid header comprising a tubular wall formed with a number of apertures, the heat exchanger having a set of tubes for flow of fluid, with each tube being received sealingly in a respective one of these apertures. The tubular wall comprises two semi-cylindrical wall members assembled together sealingly through their longitudinal edges. Each aperture for receiving a respective tube comprises two slots formed in the respective wall members, extending from an edge of the latter, with lugs being cut out during formation of these slots adjacent to the base of each slot. These lugs are bent outwardly from the fluid header so as to bear on the sides of the tube. During assembly of the heat exchanger, the two wall members are brought towards each other so as to capture the ends of the tubes between them, whereby the tubes penetrate into the slots.