57
Installation and Maintenance
Service Manual
7. 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
The AP1 voltage 
detection circuit 
is at fault
Did the equipment operate 
normally before the failure 
occurs?
outdoor units
Are wires broken?
Check wiring inside 
of the indoor and 
If the fault is eliminated?
Check the communication 
circuit of the outdoor unit
The communication 
circuit is abnormal
If the fault is eliminated?
End
Replace the main board 
of 
the indoor unit
If the fault is eliminated?
Is the connection right?
Replace the main board 
AP1of the outdoor unit
wiring diagram
Check the wiring of the indoor and 
outdoor units with reference to the 
Correctly connect the 
corresponding wires for 
the indoor and outdoor 
units with reference to 
the wiring diagram