(8) Communication malfunction: (following AP1 for outdoor unit control board)
Mainly detect:
●Is there any damage for the indoor unit mainboard communication circuit? Is communication circuit damaged?
●Detect the indoor and outdoor units connection wire and indoor and outdoor units inside wiring is connect well or not, if is there any 
damage?
Fault diagnosis process:
Yes
No
Yes
No
No
Yes
No
No
Yes
No
Yes
No
Yes
Yes
Start
Did the equipment operate 
normally before the failure 
occurs?
The AP1 voltage 
detection circuit 
is at fault
Check wiring inside of 
the indoor and outdoor 
units
Are wires broken?
Check the communication 
circuit of the outdoor unit
If the fault is eliminated?
The communication 
circuit is abnormal
Replace the main board 
of 
the indoor unit
End
If the fault is eliminated?
Replace the main board 
AP1 of the outdoor unit
If the fault is eliminated?
Is the connection right?
Check the wiring of the indoor and 
outdoor units with reference to the 
wiring diagram
Correctly connect the 
corresponding wires for 
the indoor and outdoor 
units with reference to 
the wiring diagram