UA - The indoor and outdoor units are incompatible.
Daikin's installer guide lists UA when the outdoor and indoor units are not a compatible combination.
Grounded in the official Daikin FNA25~60A2VEB(9) installer reference guide error tables for commissioning and troubleshooting.
Severity
High
Display
Shown on the user interface during test run or commissioning when unit pairing is invalid.
Support first?
Often not
Models in range
FNA25A2VEB, FNA35A2VEB, FNA50A2VEB
What to do first
Start with these checks
- 1Stop operating or commissioning the system.
- 2Check the exact indoor and outdoor model combination against Daikin documentation.
- 3Have an authorised Daikin installer confirm compatibility before further use.
Likely causes
What usually sits behind this code
Indoor and outdoor unit combination is incompatible
Incorrect matched system selected during installation
Replacement component does not match the paired unit
Contact support
Contact customer support if any of these apply
- !The code appears after a unit replacement.
- !The system was newly installed or reconfigured.
- !You cannot verify model pairing from the unit nameplates.
- - UA is a compatibility fault in the official FNA-A/FNA-A9 guide.
- - This usually needs model-number verification rather than a simple reset.
Related codes
Nearby codes in this family
Source notes
Source and scope
Source: Daikin Installer Reference Guide
Official FNA-A/FNA-A9 guidance lists UA when the indoor and outdoor units are incompatible.
Last reviewed: 2026-04-19
Daikin fault handling varies by indoor and outdoor unit combination, refrigerant type, and controller. Confirm the exact model pair and full fault history with an authorised Daikin technician before replacing parts.