Error code
U8 Indoor/outdoor combination fault
Applies to 8 models
FTXF20E5V1B, FTXF25E5V1B, FTXF35E5V1B, FTXF42E5V1B, ATXF20E5V1B, ATXF25E5V1B, ATXF35E5V1B, ATXF42E5V1B
What this means
The connected indoor and outdoor units are not operating as a valid combination.
When to call a technician
This fault involves refrigerant, pressure, or electrical work that must be handled by a certified technician under EU F-gas rules. Do not attempt to open the refrigerant circuit, access mains wiring, or adjust pressure components yourself. Contact a qualified installer or servicer for this one.
See the official Daikin manualA deep link to the manufacturer's own PDF for full technical detail. We link to manuals, we never host them.