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critical Velux
Error Code Battery fault/low battery status (yellow light)
Indicates back-up batteries are not properly connected or have failed.
? What Causes This
Battery failure or improper connection.
✓ How to Fix It
Replace faulty/broken batteries; verify connections and installation adherence to guidelines.
Source: page 21 of the official manual
From the manual
This error code appears in:
Velux Kfx 210