Fujitsu · Heat pump

18 External communication error (WLAN / option adapter)

Low severity Fujitsu wall-mounted 7-15 (NA ASU/AOU type)Fujitsu slim duct ARU 7-18 (LL type)

What the control is telling you

The indoor unit stopped receiving the expected signal from an external I/O or wireless LAN adapter (UK data: 15 s without signal). The adapter LED may also flash slowly or be off. Indoor lamps: OPERATION (green) flashes 1x, TIMER (orange) flashes 8x, ECONOMY (green) flashes fast nonstop; wired remote shows 18.

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

Likely causes

Loose or wrong adapter connection
Wireless LAN adapter failure
Adapter not powered
Indoor main PCB fault

Test and repair steps

Check the cable and plug between the indoor main PCB and the adapter.
Replace the WLAN / external adapter if the connection is good.
If the code stays with a new adapter, replace the indoor main PCB.

Settings for these units

Operating range and service space · Fujitsu multi-zone outdoor 18/24 type

Other codes on the same units

11 Serial communication error (indoor/outdoor)
12 Wired remote controller communication error
15 Check run unfinished / airflow auto-adjust error
16 Peripheral unit / transmission PCB connection error
21 Address / refrigerant circuit setting error
22 Indoor unit capacity error
23 Combination error
24 Connection unit number error

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Source: 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.

Homeowner looking at this code? See what it means for you and when to call a technician.

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.