A check valve includes a housing, a hinge pin connected to the housing, and a flap with a cam surface having stability points, the flap rotatably connected to the hinge pin. The check valve further includes a stop pin connected to the housing, a spring mounted on the stop pin, the spring having an arm, and a detent element mounted on the arm of the spring. The spring urges the detent element to be in contact with the cam surface and the flap is stable when the detent element is located at one of the plurality of stability points.