A Rotork electric actuator developed a "harmless but unnerving" fault: the LCD went dark, yet open and close worked perfectly both remotely and locally. Valve function was unaffected, but with no position indication or alarm messages visible, operators felt they were running blind.
The discussion quickly formed the correct reasoning chain: the valve opens and closes normally, which means the power board and the main control functions are healthy — the Rotork display is fed from the internal 24 V DC supply, and if the power board had failed, switching would have died long before the display. The fault zone therefore narrows to the display components themselves.
1. Loose connectors (check first, zero cost): open the actuator and check the board behind the display and its pins for poor contact — loose pins are the most common cause;
2. Identify the generation: on second-generation models the display sits on the main board; on third-generation models it is in the hood — know which generation you have before hunting for parts;
3. Flex cable: if the pins are fine, inspect the connecting flex cable; replace if damaged;
4. The display itself: once the above are cleared, the display is broken (high temperature accelerates display aging) — replace it;
5. While at it, check the battery — some alarms and parameter retention depend on it, and it is cheap to renew.
For "display dark but functions normal," the value judgment is simple: the display serves people, the functions serve the process, and their circuits are independent. Use the fact that functions work to infer the supply and main control are healthy, then narrow down to the pin–flex–display trio — ten minutes to a diagnosis. One caution: although the fault does not affect motion, an operator without position indication and alarms is effectively blind; repair it promptly and do not run it long in this state.
