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Fujitsu · Heat pump

11 Serial communication error (indoor/outdoor)

High severity Fujitsu ductless split/multi/VRF (general code list)Fujitsu wall-mounted 7-15 (NA ASU/AOU type)Fujitsu slim duct ARU 7-18 (LL type)

What the control is telling you

Indoor and outdoor boards are not hearing each other on the connection cable. On the UK service data the indoor unit flags it when no signal arrives from outdoor for over 2 min after power-up or 15 s in operation; the outdoor flags it after 10 s without indoor signal. Indoor lamps: OPERATION (green) flashes 1x, TIMER (orange) flashes 1x, ECONOMY (green) flashes fast nonstop; wired remote shows 11.

Applies to: Fujitsu ductless heat pumps: Fujitsu ductless split/multi/VRF (general code list), Fujitsu wall-mounted 7-15 (NA ASU/AOU type), Fujitsu slim duct ARU 7-18 (LL type)

Likely causes

  • Loose, wrong or broken wire on terminals 1-2-3
  • Supply voltage out of range
  • Electrical noise / poor ground
  • Indoor or outdoor main PCB failure
  • Outdoor or indoor fan motor dragging down the circuit

Test and repair steps

  1. Reset power and run; if it does not return, check for outside causes (ground, noise sources near the cable).
  2. Check the 1-2-3 connection cable at both units for loose screws, swapped wires or damage; correct per the install manual.
  3. Check supply voltage at the outdoor terminal block (NA units: 208/230 V, keep within 187-253 V).
  4. Check the signal on terminals 1-3 (should swing, UK data shows roughly AC 90-270 V) and 2-3 (roughly AC 30-130 V).
  5. If the reverse signal is bad, test the outdoor fan motor; a failed fan motor can take out the main PCB - replace both if so.
  6. If wiring, voltage and fan are good, replace the main PCB on the side that is not sending.

Settings for these units

Other codes on the same units

  • 5U Indoor unit error (general)
  • 6A Display PCB micro communication error
  • 9A Expansion valve coil error
  • 9U Outdoor unit error (general)
  • 12 Wired remote controller communication error
  • 14 Network communication error
  • 15 Check run unfinished / airflow auto-adjust error
  • 16 Peripheral unit / transmission PCB connection error

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Source: Fujitsu All Fujitsu split - multi - VRF (generic code list) codes.pdf - section error code table (indoor LED flashes); Fujitsu Wall-mounted 7-9-12-15 (North American trilingual, UTY-RNNUM remotes; e.g. ASU9-12-15 RLF1-RLS familie.pdf - section 14 Error codes; Fujitsu Wall-mounted KMCG (ASEH-AOEH 07-14) - Fujitsu UK; same error-code scheme as NA ASU-AOU units service S.pdf - section 3 Troubleshooting, 2 Troubleshooting with error code; Fujitsu Slim duct AR07-09-12-14-18 (ARU-ARYG LL-type equivalent) installation P-N 9381858064.pdf - section 14 Error codes. Summarized in our own words; check the original manual for your model.

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For licensed technicians. Gas, electrical and refrigerant work must be done by a qualified, licensed person. Shut off power and gas before servicing, never bypass a safety control, and follow the manufacturer’s manual for the exact model; it and local codes always take priority. HVACopedia is not affiliated with any manufacturer; brand and model names only identify the equipment.