The Rotork IQ series is one of the most widely used intelligent electric actuators in power plants. The reference table below is compiled from the long-term maintenance experience of power plant technicians, arranged item by item in a "symptom → check/fix" format covering 28 common problems — valve stem output, limits, position indication, modulation hunting, power supply, and display — usable as a quick field troubleshooting index.
Note before use: menu items and terminal numbers may differ between batches and firmware versions; always confirm against the manual of the specific unit, and when replacing boards, remember to save the device parameters first.
1. Valve stem has no output: A. Check whether manual operation works — if the hand/auto clutch is stuck in manual, the motor only spins idle; B. Check whether the motor turns; C. If neither manual nor electric operation works, suspect a jammed valve; D. Disconnect the valve coupling — if the valve is not jammed, check whether the sleeve is seized, stripped, or loose.
2. Cannot hold the set travel position at full open/close; the stem slams into the valve body: the "close/open limit LC/LO" parameter has been lost — re-set it, or change the parameter from "torque open/close" to "limit open/close."
3. Displayed position disagrees with actual position; drifts again after re-setting limits: replace the counter board.
4. Actuator runs but shows no position: check the counter — the round magnet or the counter board may be failed; if terminals 22/23 deliver no 4-20 mA output, consider replacing the (servo+) position feedback board.
5. Hunting up and down in remote modulation without settling: increase the dead-band parameter Fd; if hunting only stops above Fd = 20, replace the (servo+) position feedback board; if the fault persists after replacement, fit a lower-speed motor or enlarge the thread pitch between sleeve and stem.
6. No action in remote or local, or the motor turns one way only without limiting: check that the hand/auto clutch is not stuck and the motor is not burned; verify the motor power wiring and three-phase balance.
7. No action in remote or local; motor winding, thermal protection, or electromagnetic feedback measures open: the motor is burned out.
8. No action in remote or local; the setting tool shows "H1 torque switch tripped" and "H6 no electromagnetic feedback": the (solid-state) relay has no output — replace the relay control board or the power board assembly.
9. Supply breaker trips the moment three-phase power is applied: a faulty relay control board or burned motor windings.
10. Fuse blows repeatedly due to supply voltage above 400 V: with the power board's silicon rectifier block normal, the transformer primary resistance is too low — replace the power board assembly or the power transformer.
11. Backlight dark with three-phase supply normal: the actuator fuse may be blown, or the main board power connector is loose.
12. Everything normal unloaded; under load, opening works but closing stops around 40% (close torque already set to 99; the hand wheel can close it fully): if it closed properly when new but not after some service, step up one actuator size.
13. Manual works, but it will not switch to electric: the clutch retaining spring is stuck in the manual direction — remove the hand wheel, release the spring, reassemble.
14. No action in remote or local; open/close limit LEDs flash: check for a low battery — the parameters were lost during a main-power outage; replace the battery and re-set.
15. Motion normal but no position feedback: terminals 22/23 deliver only 1–3 mA; if re-setting does not help, replace the (servo+) position feedback board; if disconnecting the feedback loop restores a normal signal, the external cable is faulty — replace the cable.
16. Torque protection trips during motion and persists even with increased torque settings: check whether the actuator grease has dried out and whether the valve is jammed.
17. Valve will not fully close; still fails after re-setting the travel limit: the valve is damaged.
18. Setting and motion normal, but it cannot pass a certain position: valve sticking, or the gear-reducer mechanical limit is set backwards; check manually and re-set.
19. Motor vibrates during motion, starts and stops, runs slow: with the hand/auto clutch cleared, replace the (solid-state) relay and re-check.
20. In hand/auto, displayed position and feedback both frozen; the "limit open/close LO/LC" parameters cannot be set: the main board is dead — replace it.
21. After fitting a new power board, its silicon rectifier block heats up rapidly at power-on: components on the main board are burned — replace the main board.
22. No action in remote or local; accepts no setting signal; position displays in manual: replace the main board and the relay control board; possibly a failed switch — the magnet inside broken or missing.
23. Remote normal; selecting local immediately raises "actuator alarm": replace the local control board.
24. Remote dead, local works, but the displayed position does not change: loose connector — after re-seating everything else is normal yet remote still fails; replace the (servo+) position feedback board.
25. Local normal; remote cannot close; in remote open, the actuator runs to full open regardless of signal magnitude: re-setting limits does not help — replace the (servo+) position feedback board.
26. A new IQ MK2 shows the "valve alarm" symbol, clearable manually; in local forward/reverse the relay trips immediately: open the motor and replace the torque sensor.
27. Backlight dark, garbled symbols, or all three status LEDs lit together: replace the main board; if the run LED and the open/close limit LEDs light together, the limit setting contradicts the valve rotation direction — re-set.
28. Some alarm contacts will not change over; remote/local status cannot be detected: replace the main board or the input/output processing board.
Beyond the list, many faults stem from improper installation, setting, or operation, and several often appear mixed together — analyze them one by one with the "alarm display" and the "H help display."
