Abstract: A valve is provided with a means for determining the operability of the valve without causing it to change fluid conduction state. A spool member is axially moveable within a valve housing in response to pressure changes caused by the plunger of a pilot valve. The plunger is moved in response to an electromagnetic field induced by a solenoid coil. The coil is sequentially actuated at ever increasing intervals of time while the movement of the spool member is monitored by observing an output from a magnetically sensitive device which can be affected by the presence of a permanent magnet within its zone of detection. The permanent magnet is attached for movement with the spool member and the magnetically sensitive device, such as a Hall effect element, is attached to a stationary portion of the valve at a predetermined location.