A control assembly for converting a “fail-close” regulator to a “fail-open” regulator, or vice versa, without having to modify or reconfigure a casing of the regulator includes a control member, a central rod, and a spring disposed between first and second spring seats. A regulator including the control assembly includes a valve body and an actuator casing, the valve body defining a fluid flow-path. The control member is slidably disposed within the actuator casing and adapted for displacement relative to the valve body for controlling the flow of fluid through the flow-path. The spring and spring seats are disposed about the central rod, such that the spring biases the control member into a predetermined position relative to the regulator casing.