A: The troubleshooting steps are as follows:
1.  Check the Normally Open/Normally Closed Contact Settings: First, verify if the unit's contact settings are correct. Confirm the signal feedback terminal type of the fan using the wiring diagram, and ensure it matches the DI (Digital Input) settings. Correct any discrepancies if found. (This issue commonly occurs during initial startup or after fan maintenance.)
2.  Inspect the Signal Cable Connection: Check the signal cable connections. Ensure the fan's signal feedback terminal is connected to the controller's DI1 port and that the control signal has a 0-10V output. Verify all connections are secure without any looseness.
3.  Inspect the Power Cable Connection: Check the power cable connections. Confirm the fan's power cables are correctly and securely connected, with all terminals properly tightened.
4.  Replace the Fan: If all the above steps are confirmed correct and the issue persists, proceed to replace the fan.