Nobu NBL4-18IDU32 Service Manual page 60

(8) Malfunction of Communication (E6)
Main check point:
Check whether connection wires between indoor unit and outdoor unit and wiring inside the unit are connected well?
Check the main board of indoor unit or main board of outdoor unit is damaged?
Malfunction diagnosis process:
Communication malfunction
De-energize the unit and then
check whether connection wires
between indoor unit and outdoor
unit and wiring inside the electric
box are correct
Are wires are connected correctly?
Yes
Replace main board of indoor unit
Is malfunction eliminated?
Yes
End
74
56
Connect wire correctly
No
according to circuit
diagram
No
Replace main board
of outdoor unit
Service Manual
Service Manual
Is malfunction eliminated?
No
Installation and Maintenance
Installation and Maintenance
Yes