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Daikin · Split air conditioners · Daikin Sensira FTXF-E / ATXF-E (wall-mounted split, R32)

U4Signal transmission error (between indoor and outdoor unit)

Name in the manufacturer's documentation (user manual): Signal transmission error (between indoor and outdoor unit)[1]

In plain words (editorial)

Signal transmission error between the indoor and outdoor units. The service manual lists the power supply, the wiring between the units, the PCBs or the outdoor fan motor.

When to call a service technician: The checks listed by the service manual need the unit opened – call a service technician.

✎ editorial – written from the cited sources, not a manufacturer statement. Status: draft.

The Polish page has more detail (plain-language explanation, safe checks, guides): Read in Polish →

Sources

Every statement has a footnote to the document and PDF page. “Quote verified” means the quote was found automatically in the text of that page.

⚠ Some information comes from unofficial sources (copies shared by users, transcriptions, forums). They are marked below. Check them against the manufacturer's documentation before working on the device.

  1. [1] Daikin – User reference guide FTXF20~42E5V1B + ATXF20~42E5V1B, 4D526466-14K (2022.09) (4DEN526466-14K) , p. 36 official manufacturer document checked manually Signal transmission error (between indoor and outdoor unit)
  2. [2] Daikin – Service manual Split Sensira R32 FTXF20~71A + FTXF20~25B + FTXF20~42C (+ ATXF/RXF/ARXF), ESIE18-12E – 2021.02 – text capture of pp. 2–36 from easymanua.ls (ESIE18-12E) , p. 27 ⚠ unofficial source quote verified Faulty or disturbance of the power supply (imbalance >4%)
  3. [3] Daikin – Service manual Split Sensira R32 FTXF20~71A + FTXF20~25B + FTXF20~42C (+ ATXF/RXF/ARXF), ESIE18-12E – 2021.02 – text capture of pp. 2–36 from easymanua.ls (ESIE18-12E) , p. 27 ⚠ unofficial source quote verified Faulty wiring between the outdoor unit and the indoor unit
  4. [4] Daikin – Service manual Split Sensira R32 FTXF20~71A + FTXF20~25B + FTXF20~42C (+ ATXF/RXF/ARXF), ESIE18-12E – 2021.02 – text capture of pp. 2–36 from easymanua.ls (ESIE18-12E) , p. 27 ⚠ unofficial source quote verified Possible cause: Faulty main PCB
  5. [5] Daikin – Service manual Split Sensira R32 FTXF20~71A + FTXF20~25B + FTXF20~42C (+ ATXF/RXF/ARXF), ESIE18-12E – 2021.02 – text capture of pp. 2–36 from easymanua.ls (ESIE18-12E) , p. 27 ⚠ unofficial source quote verified Faulty outdoor unit fan motor
  6. [6] Daikin – Service manual Split Sensira R32 FTXF20~71A + FTXF20~25B + FTXF20~42C (+ ATXF/RXF/ARXF), ESIE18-12E – 2021.02 – text capture of pp. 2–36 from easymanua.ls (ESIE18-12E) , p. 27 ⚠ unofficial source quote verified Faulty indoor unit main PCB
  7. [7] Daikin – Service manual Split Sensira R32 FTXF20~71A + FTXF20~25B + FTXF20~42C (+ ATXF/RXF/ARXF), ESIE18-12E – 2021.02 – text capture of pp. 2–36 from easymanua.ls (ESIE18-12E) , p. 27 ⚠ unofficial source quote verified Check if the power supply is conform with the regulations
  8. [8] Daikin – Service manual Split Sensira R32 FTXF20~71A + FTXF20~25B + FTXF20~42C (+ ATXF/RXF/ARXF), ESIE18-12E – 2021.02 – text capture of pp. 2–36 from easymanua.ls (ESIE18-12E) , p. 27 ⚠ unofficial source quote verified Perform a check of the power supply, connections, wiring
  9. [9] Daikin – Service manual Split Sensira R32 FTXF20~71A + FTXF20~25B + FTXF20~42C (+ ATXF/RXF/ARXF), ESIE18-12E – 2021.02 – text capture of pp. 2–36 from easymanua.ls (ESIE18-12E) , p. 27 ⚠ unofficial source quote verified Perform a check of the indoor unit main PCB
  10. [10] Daikin – Service manual Split Sensira R32 FTXF20~71A + FTXF20~25B + FTXF20~42C (+ ATXF/RXF/ARXF), ESIE18-12E – 2021.02 – text capture of pp. 2–36 from easymanua.ls (ESIE18-12E) , p. 8 ⚠ unofficial source quote verified It is recommended to perform the checks in the listed order
  11. [11] Daikin – Service manual Split Sensira R32 FTXF20~71A + FTXF20~25B + FTXF20~42C (+ ATXF/RXF/ARXF), ESIE18-12E – 2021.02 – text capture of pp. 2–36 from easymanua.ls (ESIE18-12E) , p. 8 ⚠ unofficial source quote verified contact the helpdesk
  12. [12] Daikin – Service manual Split Sensira R32 FTXF20~71A + FTXF20~25B + FTXF20~42C (+ ATXF/RXF/ARXF), ESIE18-12E – 2021.02 – text capture of pp. 2–36 from easymanua.ls (ESIE18-12E) , p. 11 ⚠ unofficial source quote verified Wait for at least 10 minutes after the circuit breaker has been turned OFF