Error code
E: 18 External communication error
Applies to 6 models
ASUG09LZAS, ASUG12LZAS, ASUG15LZAS, AOUG09LZAH1, AOUG12LZAH1, AOUG15LZAH1
What this means
Communication failure involving an external input/output PCB, wireless LAN adapter, wireless LAN router, or indoor controller PCB. The family also uses E: 18 for WLAN adapter communication failure and WLAN adapter non-energized conditions.
When to call a technician
This fault involves refrigerant, pressure, or electrical work that must be handled by a certified technician under EU F-gas rules. Do not attempt to open the refrigerant circuit, access mains wiring, or adjust pressure components yourself. Contact a qualified installer or servicer for this one.