Overvoltage or voltage shortage / Synchronous signal error

What does U9 mean?

This fault is detected when DC bus voltage decreases to 210V, momentarily drops to 200V, rises to 400V, or if input current drops to 0.4A (when frequency >= 30Hz or compressor current >= 1A) during compressor operation. It signals significant power supply instability or a fault within the main circuit components like the noise filter or ACT module. Unresolved, this can lead to severe damage to the compressor and other sensitive electronic components due to improper voltage conditions.

Complete Troubleshooting Guide

1. 1

   Inspect the facility's power supply for stable voltage and adequate capacity.

2. 2

   Correct any loose, disconnected, or reversed U·V·W phase wiring to the compressor. Refer to Section 10-9 for details.

3. 3

   Check all relevant connector wirings, specifically CN00C, CNAF, CN01, and CN02, for loose connections or disconnections.

4. 4

   Test and replace the noise filter circuit board or the ACT module if suspect.

5. 5

   If all other checks pass, replace the outdoor power circuit board.