- HVAC
- Air conditioner
J6
Daikin J6 on an air conditioner: outdoor exchanger sensor fault
Risk level
Medium
Proceed carefully and stop if the check is unclear.
Urgency
Medium
Quick answer
On Daikin splits, J6 means a fault in the outdoor unit heat exchanger thermistor. That sensor takes part in control and in high pressure protection: verify the code with the remote and call a certified refrigeration technician.
Safety first
Stop and check this first
- Daikin's service manual warns that the capacitor can hold high voltage and that the split must not be started or stopped by plugging in the cable. Faced with J6, do not remove outdoor unit panels.
- Per the FTXJ-A guide, clearing J6 without knowing the cause is not advised: resetting the code belongs to a licensed installer or your dealer.
Safe checks you can perform
- Confirm J6 with the remote
- Relate J6 to the operating mode
- Heat exchanger thermistor reading (technician)
Leave these tasks to a qualified professional
- Do not attempt this professional task: Read self-diagnosis at the end
- Do not attempt this professional task: Measure the outdoor heat exchanger thermistor
- Do not attempt this professional task: Test in cooling after the repair
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.
Read self-diagnosis at the end
What they doFinishes by checking the remote's self-diagnosis to confirm J6 has stopped appearing.
They must show youthe remote stepping through the codes with no long beep on J6.
In writingrepair date and self-diagnosis result.
Measure the outdoor heat exchanger thermistor
What they doThe technician checks the connector and measures the outdoor heat exchanger thermistor against Daikin's table before changing parts.
They must show youthe outdoor heat exchanger thermistor reading next to the Table 1 value.
In writingJ6, the resistance read, the temperature and the part replaced with the reason.
Test in cooling after the repair
What they doRuns the unit in cooling for a while, because in that mode the outdoor heat exchanger thermistor also works in high pressure protection.
They must show youthe unit cooling steadily without J6.
In writingmode tested, duration and test 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 J6 with the remote
- Who:
- you, in front of the indoor unit reporting J6 and with its remote.
- How:
- open the remote's self-diagnosis menu for your model (FTXJ-A: software version screen and button held 5 seconds; BRC52A/BRC52B: ON TIMER CANCEL or OFF TIMER CANCEL for 5 seconds) and move through the list until the unit answers with a long beep.
- Result that matters:
- the indoor unit giving its long beep precisely on J6.
- If the unit beeps long with J6 on screen, note the time and continue with the J6 checks.
- If the long beep does not match J6, find the code that does trigger it, because the fault is a different one.
- Evidence to keep:
- a photo of the remote with J6 and a note of the date and 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
Relate J6 to the operating mode
- Who:
- you, keeping every panel of the unit closed.
- How:
- note whether J6 appears in cooling or heating, at start-up or after a while running, and whether the unit stops or loses power before the alert.
- Result that matters:
- giving the technician context, because Daikin uses the outdoor heat exchanger thermistor more in cooling.
- If J6 shows mostly in cooling, tell the technician:
- in that mode the sensor also guards against high pressure.
- If J6 shows equally in both modes, the technician will start with the connector and the thermistor reading.
- Evidence to keep:
- a note of every J6 alert with mode, point in the cycle and how the unit behaved.
Evidence: Daikin service manual SM-5WM-Y-NA-B1: inverter wall mounted single split FTK(X)B and FTK(X)N AXVJU
Heat exchanger thermistor reading (technician)
- Who:
- certified refrigeration technician checking the J6 alert with a meter.
- How:
- with power off, unplugs the heat exchanger thermistor at the outdoor PCB and measures its resistance with a meter, comparing it with Table 1 (20 kΩ at 25 °C) in Daikin's Appendix A.
- Result that matters:
- a resistance value that does or does not fit the real outdoor heat exchanger temperature.
- If the heat exchanger thermistor does not fit the table, it is replaced and the test repeated.
- If the heat exchanger thermistor fits and J6 returns, the outdoor PCB is checked.
- Evidence to keep:
- a report with the resistance read, the reference temperature and the part replaced.
Needs the outdoor unit opened, with mains voltage and charged capacitors: 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 J6
What it means
In the Daikin FTXJ-A installer reference guide, J6 is "Outdoor unit: Malfunction of heat exchanger thermistor". The FTK(X)B and FTK(X)N service manual describes it as an outdoor heat exchanger thermistor abnormality and explains that this sensor sets the target discharge temperature and, in cooling, is used for high pressure protection. On other Daikin models J6 may mean something different. J6 by itself never proves which part has failed.
Warnings and stop conditions
- Higheditorial warning
Daikin's service manual warns that the capacitor can hold high voltage and that the split must not be started or stopped by plugging in the cable. Faced with J6, do not remove outdoor unit panels.
Evidence: Daikin service manual SM-5WM-Y-NA-B1: inverter wall mounted single split FTK(X)B and FTK(X)N AXVJU
- Mediumsource verified
Per the FTXJ-A guide, clearing J6 without knowing the cause is not advised: resetting the code belongs to a licensed installer or your dealer.
Evidence: Daikin FTXJ-A installer reference guide — English
Symptoms and causes
Probable causes · in order
- Heat exchanger thermistor connectorCommon
Daikin lists connector disconnection first; a badly plugged outdoor heat exchanger thermistor is enough to give J6.
Evidence: Daikin service manual SM-5WM-Y-NA-B1: inverter wall mounted single split FTK(X)B and FTK(X)N AXVJU
- Outdoor heat exchanger thermistorPossible
If its resistance does not match the 20 kΩ table in Appendix A, the flowchart says to replace the outdoor heat exchanger thermistor.
Evidence: Daikin service manual SM-5WM-Y-NA-B1: inverter wall mounted single split FTK(X)B and FTK(X)N AXVJU
- Defective outdoor PCBPossible
With the heat exchanger thermistor reading correctly and J6 back, Daikin's flowchart ends at the outdoor unit PCB.
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 J6 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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