Abstract: A pressure control assembly having a snap-acting Belleville washer responsive to fluid pressure, and a switch actuating mechanism movable therewith, includes an adjusting mechanism for the snap-acting Belleville washer. The adjusting mechanism includes at least one pin which can be moved along the surface of the Belleville washer to change the Belleville washer's pivot point by increasing or decreasing its lever arm, thus varying its snap pressure. In the preferred embodiment, there are three pins which extend through aligned slots in an upper and lower plate and the pins can be moved radially inwardly and outwardly by rotating the lower plate relative to the upper plate.