A0 - The system has detected a refrigerant leak.
Daikin's installer reference guide lists A0 as a refrigerant leak detected condition during commissioning or fault diagnosis.
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 troubleshooting.
Support first?
Often not
Models in range
FNA25A2VEB, FNA35A2VEB, FNA50A2VEB
What to do first
Start with these checks
- 1Stop operating the system.
- 2Ventilate the area if refrigerant leakage is suspected.
- 3Arrange inspection by an authorised Daikin installer.
Likely causes
What usually sits behind this code
Refrigerant leak detected by the system
Leak-related protection triggered after installation or service work
Contact support
Contact customer support if any of these apply
- !The code appears more than once.
- !You notice refrigerant smell, hissing, or reduced cooling/heating performance.
- !The unit was recently installed, moved, or serviced.
- - The guide marks this code as applicable to units using R32 refrigerant.
- - Daikin presents this as a protection condition, not a user-reset maintenance reminder.
Related codes
Nearby codes in this family
Source notes
Source and scope
Source: Daikin Installer Reference Guide
Official FNA-A/FNA-A9 guidance lists A0 as refrigerant leak detected.
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.