Daikin mini split error code UA
Indoor and outdoor unit combination mismatch.
- TypeFault
- SystemOperation
- Can I fix it?Homeowner checks, then maybe a tech
What UA means on a Daikin
The indoor and outdoor units are not a compatible pairing, or a board is set for the wrong model.
On this platform, UA is a fault: something has failed or is disconnected and needs diagnosis.
Common causes
- Units from different series or capacities paired together.
- An unsupported multi-split combination.
- A replacement board not configured for the model.
How to fix it yourself
Work through the checks below first; they resolve most cases. If they do not, the repair itself may need a technician.
- Check the model numbers against Daikin's compatibility list.
- Reset the system: switch the breaker (or the outdoor disconnect) off, wait a full five minutes so the boards fully discharge, then switch it back on and restart from the remote.
Switch off power at the breaker before opening either unit. Capacitors in the outdoor unit hold a charge for several minutes after power is cut.
When to call a technician
If the pairing is valid, a technician needs to check the board settings.
Which Daikin units show UA
This page applies to Daikin Aurora, 19 Series, Atmosphera, Emura, Quaternity and MXS multi-zone units. Daikin's own documentation lists UA as "Indoor and outdoor unit combination mismatch", the same definition used across the Daikin it is built on. If your unit shows a code with a different shape (for example a four-character code, or a plain number), it is from a different table; use the lookup with your exact code.
Where Daikin shows this code
Most Daikin wall units do not show the code on the unit; the operation lamp blinks. To read the code, point the remote at the unit, hold CANCEL (or Timer Cancel) for about 5 seconds until 00 shows, then press CANCEL repeatedly. Each press shows a code; when the unit gives a long continuous beep instead of two short beeps, the code on the remote is the stored fault. Units with a wired controller show the code directly. A and C codes are indoor-unit faults, E, F, H, J, L and P codes are outdoor-unit faults and protections, and U codes are system-level problems such as communication, power supply and refrigerant shortage.
Other Daikin codes
Same part of the system as UA:
UA on other brands
The same characters do not always mean the same thing. Check the brand on your unit.
- Goodman UA Indoor and outdoor unit combination mismatch
Questions people ask
Can I reset a Daikin UA code myself?
Yes. Turn the system off at the breaker for five minutes, then restart it. If UA comes back, the fault is real and needs the checks above.
Is it safe to keep running a Daikin showing UA?
The unit will usually refuse to run, or run with reduced output, until the fault is cleared. Repeated resets do not fix anything and can mask a problem that is getting worse.
Do I need a technician for Daikin UA?
Work through the checks below first; they resolve most cases. If they do not, the repair itself may need a technician. If the pairing is valid, a technician needs to check the board settings.
Sources
- Daikin residential (RA) service manuals (error code tables)
- Daikin operation manuals (remote controller self-diagnosis)
Updated September 2026. Codes and definitions vary by model year. If your manual disagrees with this page, your manual wins. Send a correction.