Abstract: A magnetic differential pressure valve is provided, having an indicator showing when the valve has moved into one of the open and closed positions, comprising a housing including a valve seat; valve means reciprocably mounted in the housing for movement towards and away from the valve seat between open and closed positions; first magnetic means movable with the valve means toward and away from the valve seat; first bias means urging the valve means and first magnetic means in one direction and normally retaining the valve means and first magnetic means in one of the closed and open positions; second magnetic means movable toward and away from the first magnetic means and normally retained in a first nonindicating position, reacting with the first magnetic means whenever the two means are within their mutually reactive magnetic fields of force, and the valve means is in one of the closed and open positions; and second bias means urging the second magnetic means into one of the nonindicating and indicating posi