A fluid switching device (1) for a valve having at least three ports, the device (1) comprising: a flap (10) capable of pivoting between a first position in which it blocks a first port (9) and a second position in which it blocks a second port (11), an actuating member (2) for actuating the flap (10), capable of moving the flap (10) from one blocking position to the other, the device (1) comprising an interface part (12) capable of interacting with the actuating member (2), the device (1) being configured in such a way that this interaction selectively allows the flap (10) to be moved by the actuating member (2) and selectively allows the flap (10) to be held in position, the actuating member (2) moving the flap (10) via a guide path (14) provided in the interface part (12).