54
Installation and Maintenance
Service Manual
7.Communication malfunction (AP1 below is control board of outdoor unit)
Main detection point:
● Check if the connection wire and the built-in wiring of indoor and outdoor unit is connected well and no damaged;
● If the communication circuit of indoor mainboard  is damaged? If the communication circuit of  outdoor mainboard (AP1) is dam-
aged
Malfunction diagnosis process:
Start
Check communication 
circuit of outdoor unit
Problem of 
communication 
circuit
Check built-
in wiring of 
indoor and 
outdoor unit
Connection 
correct?
Malfunction of
circuit is 
detected with 
control board 
AP1 voltage
Check connection 
wire of indoor and 
outdoor unit with 
circuit diagram
Check connection
wire of indoor and 
outdoor unit with 
circuit diagram
If the unit is operation 
normal before malfunction
Y
N
Y
N
If the wiring is 
damaged?
If the malfunction 
is removed?
N
Y
N
If the malfunction 
is removed?
N
Replace indoor 
board
Replace outdoor 
mainboardAP11
If the 
malfunction is 
removed?
Y
N
Y
N
Y
Y
End