DCS signal is ok, but the valve is not opening. Fuse is ok, ohm is okay, but the valve isn’t opening and why is that
Possible fault: Valve body jam, Valve actuator jam, the loose connection in SOV, coil fault. Check SOV output port and valve stem body, whether you get Instrument air from sov output, you can check actuator, if torque is required for that add one spring inside the actuator. Do trouble shooting and check loop, air supply, logic. if all the things are ok then the valve could be stuck from inside