A three-port valve (1, 1') comprising: · a casing (2, 2') presenting a fluid inlet (3, 3'), first and second fluid outlets (4, 5; 4', 5'), a first fluid-flow passage (6, 6') between the fluid inlet (3, 3') and the first fluid outlet (4, 4'), and a second fluid-flow passage (7, 7') between the first and second fluid outlets (4, 5; 4', 5'); and · a movable element (8, 8') received in the casing (2, 2') and comprising: · a rod (9, 9'); · a first valve member (10, 10') fastened to a first end of the rod (9, 9') and suitable for being received towards the rod (9, 9') in a first valve seat (12, 12') for closing the first fluid-flow passage (6, 6'); and · a second valve member (11, 11') fastened to a second end of the rod (9, 9') and suitable for being received towards the rod (9, 9') in a second valve seat of the casing for closing the second fluid-flow passage (7, 7'), the length of the rod (9, 9') enabling the movable element (8, 8') to move between a first position in which the first passage (6, 6') is closed and the second passage (7, 7') is open, and a second position in which the first passage (6, 6') is open and the second passage (7, 7') is closed; the valve being characterized in that it also includes at least one diaphragm spring (16, 16') supporting the movable element (8, 8') in a plane substantially perpendicular to a movement axis between the first and second positions. · a casing (2, 2') presenting a fluid inlet (3, 3'), first and second fluid outlets (4, 5; 4', 5'), a first fluid-flow passage (6, 6') between the fluid inlet (3, 3') and the first fluid outlet (4, 4'), and a second fluid-flow passage (7, 7') between the first and second fluid outlets (4, 5; 4', 5'); and · a movable element (8, 8') received in the casing (2, 2') and comprising: · a rod (9, 9'); · a first valve member (10, 10') fastened to a first end of the rod (9, 9') and suitable for being received towards the rod (9, 9') in a first valve seat (12, 12') for closing the first fluid-flow passage (6, 6'); and · a second valve member (11, 11') fastened to a second end of the rod (9, 9') and suitable for being received towards the rod (9, 9') in a second valve seat of the casing for closing the second fluid-flow passage (7, 7'), the length of the rod (9, 9') enabling the movable element (8, 8') to move between a first position in which the first passage (6, 6') is closed and the second passage (7, 7') is open, and a second position in which the first passage (6, 6') is open and the second passage (7, 7') is closed; · a rod (9, 9'); · a first valve member (10, 10') fastened to a first end of the rod (9, 9') and suitable for being received towards the rod (9, 9') in a first valve seat (12, 12') for closing the first fluid-flow passage (6, 6'); and · a second valve member (11, 11') fastened to a second end of the rod (9, 9') and suitable for being received towards the rod (9, 9') in a second valve seat of the casing for closing the second fluid-flow passage (7, 7'), the length of the rod (9, 9') enabling the movable element (8, 8') to move between a first position in which the first passage (6, 6') is closed and the second passage (7, 7') is open, and a second position in which the first passage (6, 6') is open and the second passage (7, 7') is closed;