York DHP30NWB21SDCP30NWB21SDHP36NWB21SDCP36NWB21S Service Manual page 63

(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
Y
detection circuit
is at fault
If the fault is eliminated?
N
Y
Did the equipment operate
normally before the failure
Y
Check wiring inside of
the indoor and outdoor
units
Are wires broken?
N
Check the communication
circuit of the outdoor unit
The communication
Y
circuit is abnormal
N
N
Replace the main board
of the indoor unit
Start
occurs?
Y
N
Replace the main board
AP1 of the outdoor unit
If the fault is eliminated?
Y
End
N
Check the wiring of the indoor and
outdoor units with reference to the
wiring diagram
Is the connection right?
N
Correctly connect the
corresponding wires for
the indoor and outdoor
units with reference to
the wiring diagram
If the fault is eliminated?
Y
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