Cause: Reference encoder feedback signal comes when a failure or critical issue with the reference encoder or its feedback signal. 

REFF REF ENCODER FAIL fault in Parker AC890 drive indicates a failure or issue with the reference encoder feedback signal. The reference encoder typically measures the position or speed of the load or another aspect of the system, depending on the application. This fault means that the drive is unable to correctly read or interpret the signal from the reference encoder.

Troubleshooting Steps:

• Visually examine the encoder for any signs of physical damage.
• Carefully inspect the entire length of the encoder cable for cuts, kinks, or abrasions.
• Using the wiring diagrams in both the AC890 drive manual and the reference encoder's datasheet, double-check that each wire is connected to the correct terminal. Pay close attention to power, ground, and signal lines (A, B, Z or U, V, W depending on the encoder type).
• Ensure the cable is securely connected at both the drive's encoder feedback terminals (typically on a dedicated option board or control board connector) and the encoder itself.