York DHP30NWB21SDCP30NWB21SDHP36NWB21SDCP36NWB21S Service Manual page 64

(9) Communication malfunction:(following AP1 for outdoor unit control board)
Mainly detect:
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?
Is there any damage for the indoor unit mainboard communication circuit? Is communication circuit damaged?
The flow chart malfunction detect:
The AP1 voltage
detection circuit
is at fault
If the fault is eliminated?
Y
57
Y
Check wiring inside of
the indoor and outdoor
units
Are wires broken?
Y
N
Check the communication
N
circuit of the outdoor unit
The communication
circuit is abnormal
N
Replace the main board of
the indoor unit
Start
Did the equipment operate
normally before the failure
occurs?
Y
Replace the main board
Y
AP1 of the outdoor unit
If the fault is eliminated?
N
Y
End
N
Check the wiring of the indoor and
outdoor units with reference to the
wiring diagram
Is the connection right?
N
N
Correctly connect the
corresponding wires for
the indoor and outdoor
units with reference to
the wiring diagram
If the fault is eliminated?
Y