Fisher FSAI-CP-90BE3 Service Manual page 69

(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:
The AP1 voltage
detection circuit
is at fault
If the fault is eliminated?
Yes
66
Yes
Check wiring inside of
the indoor and outdoor
units
Yes
Are wires broken?
No
Check the communication
No
circuit of the outdoor unit
The communication
circuit is abnormal
No
Replace the main board
of the indoor unit
Start
Did the equipment operate
normally before the failure
occurs?
Yes
Replace the main board
Yes
AP1 of the outdoor unit
If the fault is eliminated?
No
Yes
End
No
Check the wiring of the indoor and
outdoor units with reference to the
wiring diagram
Is the connection right?
No
No
Correctly connect the
corresponding wires for
the indoor and outdoor
units with reference to
the wiring diagram
If the fault is eliminated?
Yes
Installation and Maintenance
Service Manual