Daikin Packaged Unit Error Code UA

Full Diagnosis

UA is a system-configuration mismatch detected at startup — too many indoor units connected to one outdoor unit, indoor and outdoor units running incompatible refrigerant types, or outdoor PCB settings not re-entered after a board replacement — rather than a wiring or communication failure. This sets it apart from U4, which is a genuine transmission fault on correctly matched equipment, and from MA, which is a controller-combination conflict on the centralized-control network rather than the refrigerant circuit's indoor/outdoor equipment itself. The system will not start normal operation until the combination is corrected.

All Recorded Causes

Number of connected indoor units exceeds the outdoor unit's rated capacity. Refrigerant type mismatch between indoor and outdoor units. Outdoor unit PCB replaced without re-entering required field settings. Incompatible model combination for the installed system type. Defective outdoor unit PCB reporting an invalid configuration.

Verify Before Replacing Parts

1. Confirm the exact Daikin model family and packaged context before acting on a generic code description.
2. Confirm board LEDs, wiring polarity, and model compatibility before replacing control boards — this Daikin fault points at number of connected indoor units exceeds the outdoor unit's rated capacity.
3. Check for intermittent communication faults caused by connectors, moisture, or damaged harnesses, and rule out refrigerant type mismatch between indoor and outdoor units.
4. After the correction, run the system long enough to confirm the packaged fault does not return under normal load.