Fluid switchover device comprising: a housing comprising at least three ports leading into an interior space of the housing ; a valve flap comprising a rotational axis , the valve flap being rotatably arranged within the housing , and the rotational axis being mounted to the housing at a first location and being mounted to the housing at a second location ; and a circumferential seal mounted to the valve flap and comprising a first evasion portion at the first location and a second evasion portion at the second location , the first evasion portion and the second evasion portion being configured to evade the rotational axis on the same side of the valve flap , and wherein the valve flap is configured to slidingly engage a boundary of the interior space of the housing by means of the circumferential seal , so that at a first position of the valve flap , the first port is connected to the second port and the first port is sealed off from the third port , and so that in a second position of the valve flap , the first port is connected to the third port and the first port is sealed off from the second port , wherein the circumferential seal projects beyond the valve flap so as to slidingly engage the interior space of the housing , characterized in that the circumferential seal is an O ring held within an O ring holding portion of the valve flap , and the valve flap comprises a first valve flap part and a second valve flap part separated from the first valve flap part , wherein the circumferential seal is continuously in contact with the first valve flap part , wherein the rotational axis is arranged between the first valve flap part and the second valve flap part , and wherein the second valve flap part is not in contact with the circumferential seal at the first evasion portion and the second evasion portion of the circumferential seal . a housing comprising at least three ports leading into an interior space of the housing ; a valve flap comprising a rotational axis , the valve flap being rotatably arranged within the housing , and the rotational axis being mounted to the housing at a first location and being mounted to the housing at a second location ; and a circumferential seal mounted to the valve flap and comprising a first evasion portion at the first location and a second evasion portion at the second location , the first evasion portion and the second evasion portion being configured to evade the rotational axis on the same side of the valve flap , and wherein the valve flap is configured to slidingly engage a boundary of the interior space of the housing by means of the circumferential seal , so that at a first position of the valve flap , the first port is connected to the second port and the first port is sealed off from the third port , and so that in a second position of the valve flap , the first port is connected to the third port and the first port is sealed off from the second port , wherein the circumferential seal projects beyond the valve flap so as to slidingly engage the interior space of the housing , characterized in that the circumferential seal is an O ring held within an O ring holding portion of the valve flap , and the valve flap comprises a first valve flap part and a second valve flap part separated from the first valve flap part , wherein the circumferential seal is continuously in contact with the first valve flap part , wherein the rotational axis is arranged between the first valve flap part and the second valve flap part , and wherein the second valve flap part is not in contact with the circumferential seal at the first evasion portion and the second evasion portion of the circumferential seal . <EOS>