- HVAC
- Air conditioner
UA
Daikin UA on an air conditioner: indoor and outdoor unit mismatch
Risk level
Medium
Proceed carefully and stop if the check is unclear.
Urgency
Medium
Quick answer
On Daikin splits, UA means a mismatch between the indoor and outdoor units (installation abnormality). It is usually seen after an installation or repair: confirm the code, gather both unit models and call the installer.
Safety first
Stop and check this first
- Daikin's service manual warns not to start or stop the unit by plugging and unplugging the power cable, because of shock or fire risk, and that the outdoor unit capacitor can hold high voltage. Do not open the outdoor unit or the indoor casing: that is the technician's job.
- If UA appears after an installation, the fault lies in the installation: ask whoever did it to check it, with both unit models in writing.
Safe checks you can perform
- Confirm the code with the remote
- Link the code to recent work
- Read the labels without opening anything
- Combination, wiring and boards (technician)
Leave these tasks to a qualified professional
- Do not attempt this professional task: Verify the combination first
- Do not attempt this professional task: Check wires and part numbers
- Do not attempt this professional task: Test after correcting
What a technician must be able to justify
Technician visit
These are the steps they must carry out and show you. Tick them as they work: if steps are skipped, do not accept a part swap.
These are not instructions for opening or handling the equipment yourself. They are the checks that should support a technical conclusion.
Verify the combination first
What they doThe technician checks that the indoor and outdoor units are compatible models before touching any board.
They must show youboth unit models compared with the combination Daikin allows.
In writingthe code, the models checked and the conclusion, with the date.
Check wires and part numbers
What they doChecks the connecting wires between units and the part number of the indoor and outdoor PCBs.
They must show youeach PCB part number and the state of the connections.
In writingwhich board was replaced or which connection was corrected, and why.
Test after correcting
What they doRuns the unit and confirms that neither UA nor another code returns in the history.
They must show youthe unit running and the code history without UA.
In writingdate, test duration and result.
Before accepting a part or repair
Nothing has been shown yet. Do not accept a part swap based on the code alone.
Follow these steps
Note: Follow the documented order. An error code identifies the affected system, but it does not prove by itself which part has failed.
Confirm the code with the remote
- Who:
- you, with the unit switched on and the wireless remote.
- How:
- enter the remote's self-diagnosis menu as Daikin describes for your model (in the FTXJ-A guide, from the software version screen by holding the button for 5 seconds; on BRC52A and BRC52B remotes, by holding ON TIMER CANCEL or OFF TIMER CANCEL for 5 seconds) and scroll through the list aimed at the unit until you hear a long beep.
- Result that matters:
- that the long beep sounds exactly on UA.
- If the long beep sounds on UA:
- continue with this page and note when it appears.
- If it sounds on another code:
- look that code up, because each one points to a different check.
- Evidence to keep:
- a photo of the remote showing the code, the date, the time and the operating mode.
Evidence: Daikin FTXJ-A installer reference guide — English · Daikin service manual SM-5WM-Y-NA-B1: inverter wall mounted single split FTK(X)B and FTK(X)N AXVJU
Link the code to recent work
- Who:
- you, with the invoice or installation report.
- How:
- check whether UA appeared right after the unit was installed, one of the units was changed or a board was replaced, and look up each unit's model in the paperwork.
- Result that matters:
- knowing whether there was recent work and which models were installed.
- If it appeared after an installation or repair:
- contact whoever did it with the models noted.
- If it appeared without any prior work:
- tell the technician, because it points more to a faulty board.
- Evidence to keep:
- the invoice or report with both unit models and the date of the work.
Evidence: Daikin service manual SM-5WM-Y-NA-B1: inverter wall mounted single split FTK(X)B and FTK(X)N AXVJU
Read the labels without opening anything
- Who:
- you, with the unit switched off.
- How:
- read and photograph the outdoor unit rating label, and the indoor one only if it is visible without removing any part; if something has to come off, leave it to the technician.
- Result that matters:
- having the exact model of both units to check the combination.
- If you have both models:
- send them to the installer before the visit.
- If a label is not visible:
- do not open the casing; the technician will read it.
- Evidence to keep:
- photos of the model and serial number labels.
Evidence: Daikin service manual SM-5WM-Y-NA-B1: inverter wall mounted single split FTK(X)B and FTK(X)N AXVJU
Combination, wiring and boards (technician)
- Who:
- certified refrigeration technician.
- How:
- follows Daikin's flowchart: checks the indoor and outdoor combination, checks with power off that the connecting wires are connected properly and verifies the indoor and outdoor PCB part numbers.
- Result that matters:
- knowing whether the combination, the wiring or a board is at fault.
- If the combination or a board is not compatible:
- it is corrected with the right model or PCB.
- If everything is compatible and UA remains:
- the indoor or outdoor PCB is replaced, as diagnosed.
- Evidence to keep:
- a report with the models checked, the PCB part numbers and what was corrected.
Checking terminals and boards requires cutting power and opening the units: technician only.
Evidence: Daikin service manual SM-5WM-Y-NA-B1: inverter wall mounted single split FTK(X)B and FTK(X)N AXVJU
Still not solved
If the error persists, stop here. See what the technician must do and show you.
Where this code applies
A code is meaningful only inside the right product and version context.
Primary scope
- System
- HVAC
- Brand
- Daikin
- Product type
- Air conditioner
Known code variants
- Daikin UA
What it means
In the Daikin FTXJ-A installer reference guide, UA is "Indoor unit, outdoor unit mismatching problem". The FTK(X)B and FTK(X)N service manual calls it an installation abnormality and lists wrong models interconnected and a wrong or defective indoor or outdoor PCB. Other models may differ. The code alone never proves which part is faulty: the model combination and wiring are checked first.
Warnings and stop conditions
- Higheditorial warning
Daikin's service manual warns not to start or stop the unit by plugging and unplugging the power cable, because of shock or fire risk, and that the outdoor unit capacitor can hold high voltage. Do not open the outdoor unit or the indoor casing: that is the technician's job.
Evidence: Daikin service manual SM-5WM-Y-NA-B1: inverter wall mounted single split FTK(X)B and FTK(X)N AXVJU
- Mediumeditorial warning
If UA appears after an installation, the fault lies in the installation: ask whoever did it to check it, with both unit models in writing.
Evidence: Daikin service manual SM-5WM-Y-NA-B1: inverter wall mounted single split FTK(X)B and FTK(X)N AXVJU
Symptoms and causes
Probable causes · in order
- Wrong models interconnectedCommon
Daikin lists interconnecting models that are not compatible; the fix is to match compatible units.
Evidence: Daikin FTXJ-A installer reference guide — English · Daikin service manual SM-5WM-Y-NA-B1: inverter wall mounted single split FTK(X)B and FTK(X)N AXVJU
- Connecting wires not connected properlyPossible
Daikin's flowchart checks whether the wires between units are connected properly and, if not, asks to correct the connection.
Evidence: Daikin service manual SM-5WM-Y-NA-B1: inverter wall mounted single split FTK(X)B and FTK(X)N AXVJU
- Wrong or defective indoor PCBPossible
An indoor PCB that does not match the model may have been fitted, or the PCB may be defective.
Evidence: Daikin service manual SM-5WM-Y-NA-B1: inverter wall mounted single split FTK(X)B and FTK(X)N AXVJU
- Wrong or defective outdoor PCBPossible
Daikin also includes a wrong or defective outdoor PCB; it is verified against the part number.
Evidence: Daikin service manual SM-5WM-Y-NA-B1: inverter wall mounted single split FTK(X)B and FTK(X)N AXVJU
Virtual technician
Does UA still appear after these checks?
Answer a few questions to narrow down the likely cause and the safest next action. Guidance only - it never replaces a professional.
Sources and technical references
- 1
Daikin FTXJ-A installer reference guide — English
Daikin Europe N.V. · 2022 · official_doc
- 2
Daikin FTXJ-A — guía de referencia del instalador
Daikin Europe N.V. · 2022 · official_doc
- 3
Daikin service manual SM-5WM-Y-NA-B1: inverter wall mounted single split FTK(X)B and FTK(X)N AXVJU
Daikin · 2018 · official_doc
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