The Rotork IQ series is one of the most widely used intelligent electric actuators in power plants. This reference, compiled from the long-term field experience of power-plant maintenance technicians, breaks 28 common faults into five quick-reference tables in a “symptom → likely cause → check & fix” format, covering valve stem output, limits, position indication, modulation hunting, power supply, and display/alarm — find the symptom, then work through the fix column step by step.
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, save the device parameters first.
Field reminder: before replacing any board, record the unit parameters with the setting tool and restore them afterwards before judging the fault — limit, dead-band and torque settings are lost when main power fails while the backup battery is dead (items 2 and 14).
Manual first, then electric, then disconnect the valve — in that order, rule out a stuck clutch, a failed motor and a jammed valve (steps A→D of item 1).
| Table 1 Mechanical & motor faults (5 items) | |||
|---|---|---|---|
| # | Symptom | Likely cause | Check & fix |
| 1 | Valve stem has no output | Hand/auto clutch stuck in manual (motor spins idle); motor not turning; jammed valve; sleeve seized, stripped or loose | Check manual operation first, then whether the motor turns; if neither works, disconnect the valve coupling and inspect the sleeve |
| 6 | No action in remote or local, or motor turns one way only without limiting | Hand/auto clutch stuck; burned motor; wrong power wiring or unbalanced three-phase supply | Inspect clutch and motor; verify power wiring and phase balance |
| 7 | No action in remote or local; motor winding, thermal protection or electromagnetic feedback reads open | Motor burned out | Replace the motor |
| 13 | Manual works, but it will not switch to electric | Clutch retaining spring stuck in the manual direction | Remove the hand wheel, release the spring, reassemble |
| 18 | Setting and motion normal, but it cannot pass a certain position | Valve sticking; gear-reducer mechanical limit set backwards | Check manually and re-set the mechanical limit |
Position-indication and feedback fixes concentrate on two boards: the counter board (items 3-4) and the (servo) position feedback board (items 4, 15, 24, 25).
| Table 2 Limits, position display & feedback (8 items) | |||
|---|---|---|---|
| # | Symptom | Likely cause | Check & fix |
| 2 | Cannot hold the set travel position at full open/close; stem slams into the valve body | “Close/open limit LC/LO” parameter lost | Re-set the limits, 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 | Counter board failure | Replace the counter board |
| 4 | Actuator runs but shows no position | Counter round magnet or counter board failed; if terminals 22/23 deliver no 4-20 mA, the (servo) position feedback board is suspect | Check the counter magnet and board; measure 22/23 current and replace the feedback board if needed |
| 15 | Motion normal but no position feedback (22/23 loop delivers only 1-3 mA) | Position feedback board fault; or external feedback cable fault | If re-setting does not help, replace the feedback board; if the signal recovers when the loop is disconnected, the external cable is faulty — replace it |
| 17 | Valve will not fully close; still fails after re-setting the travel limit | Valve damaged | Repair or replace the valve |
| 20 | In hand/auto, displayed position and feedback both frozen; “limit open/close LO/LC” cannot be set | Main board dead | Replace the main board |
| 24 | Remote dead, local works, but displayed position does not change | Loose connector; if re-seating does not restore remote, the feedback board is faulty | Re-seat the connectors; if everything else is normal yet remote still fails, replace the position feedback board |
| 25 | Local normal; remote cannot close; in remote open it runs to full open regardless of signal | Position feedback board fault | Re-setting limits does not help — replace the (servo) position feedback board |
For hunting, adjust the dead-band first; for torque trips, check lubrication and the valve first — the checking order given by the original field table.
| Table 3 Modulation & torque faults (4 items) | |||
|---|---|---|---|
| # | Symptom | Likely cause | Check & fix |
| 5 | Hunting up and down in remote modulation without settling | Dead-band parameter Fd too small; position feedback board fault | Increase Fd; if hunting only stops above Fd = 20, replace the feedback board; if it persists after replacement, fit a lower-speed motor or enlarge the thread pitch between sleeve and stem |
| 12 | Normal unloaded; under load closing stops around 40% (close torque set to 99; hand wheel closes fully; closed fully when new but not after some service) | Actuator undersized | Step up one actuator size |
| 16 | Torque protection trips during motion and persists even with increased torque settings | Actuator grease dried out; valve jammed | Check actuator lubrication and valve condition |
| 19 | Motor vibrates during motion, starts and stops, runs slow | (Solid-state) relay fault (with the hand/auto clutch cleared) | Replace the solid-state relay and re-check |
Follow two lines: breaker trips → relay control board / motor windings; fuse blows → transformer. A dark backlight starts at the fuse and connectors.
| Table 4 Power supply, fuse & battery faults (5 items) | |||
|---|---|---|---|
| # | Symptom | Likely cause | Check & fix |
| 9 | Supply breaker trips the moment three-phase power is applied | Relay control board fault; burned motor windings | Check the relay control board and motor windings |
| 10 | Fuse blows at supply voltage above 400 V and again after replacement | With the power board silicon rectifier 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 | Actuator fuse blown; main board power connector loose | Check the fuse and re-seat the main board power connector |
| 14 | No action in remote or local; open/close limit LEDs flashing | Battery voltage low — parameters lost during a main-power outage | Replace the battery and re-set the parameters |
| 21 | After fitting a new power board, its silicon rectifier heats up rapidly at power-on | Components on the main board burned | Replace the main board |
Erratic alarms and LED anomalies are mostly main-board related; the IQ MK2 torque sensor fault has its own signature (item 26).
| Table 5 Board & alarm-signal faults (6 items) | |||
|---|---|---|---|
| # | Symptom | Likely cause | Check & fix |
| 8 | No action in remote or local; setting tool shows “H1 torque switch tripped” and “H6 no electromagnetic feedback” | (Solid-state) relay has no output | Replace the relay control board or the power board assembly |
| 22 | No action in remote or local; accepts no setting signal; position displays in manual | Main board and relay control board fault; or the switch magnet broken/missing | Replace the main board and relay control board; inspect the switch magnet |
| 23 | Remote normal; selecting local immediately raises “actuator alarm” | Local control board fault | Replace the local control board |
| 26 | A new IQ MK2 shows the “valve alarm” symbol, clearable manually; in local forward/reverse the relay trips immediately | Torque sensor fault | Open the motor and replace the torque sensor |
| 27 | Backlight dark, garbled symbols, or all three status LEDs lit together | Main board fault; if the run LED and open/close limit LEDs light together, the limit setting contradicts the valve rotation direction | Replace the main board; re-set the direction contradiction |
| 28 | Some alarm contacts will not change over; remote/local status cannot be detected | Main board or input/output processing board fault | Replace the main board or the I/O processing board |
Beyond the tables, 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.”
Need selection support, spare parts or maintenance service for Rotork IQ series actuators? Submit an RFQ, or continue with the site’s Rotork electric actuator maintenance procedures guide.
Sources: compiled from power-plant maintenance experience threads on the BJX Power Forum (post 268549454); menu items and terminal numbers follow the manual of your specific batch.
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