A device for changing a flow direction through a heat exchanger, comprising a valve housing and a rotatable valve member arranged inside the valve housing. The valve housing comprises first and second ends and a center axis (B) extending between them. The device comprises a first port, a second port, a third port and a fourth port. The first end is provided with the first port, and the second end is provided with the third and fourth ports, wherein the valve member is rotatable between a first position and a second position and, in the first position, defines a conduit between the first port and the third port and, in the second position, defines a conduit between the first port and the fourth port. The valve member is rotatable around an axis of rotation offset from the center axis (B) and extending through the center of the first port, and the first port is angularly displaced 90° around the center axis (B) in relation to the third and fourth ports.