Lennox LI018CI-180P432 Service Manual page 56

Service Manual
7.Communication malfunction (AP1 below is control board of outdoor unit)
Main detection point:
● Check if the connection wire and the built-in wiring of indoor and outdoor unit is connected well and no damaged;
● If the communication circuit of indoor mainboard is damaged? If the communication circuit of outdoor mainboard (AP1) is dam-
aged
Malfunction diagnosis process:
Malfunction of
circuit is
detected with
control board
AP1 voltage
If the malfunction
is removed?
Y
Installation and Maintenance
Y
Check built-
in wiring of
indoor and
outdoor unit
If the wiring is
Y
damaged?
N
Check communication
N
circuit of outdoor unit
Problem of
communication
circuit
N
Replace indoor
board
Start
If the unit is operation
normal before malfunction
Y
Replace outdoor
Y
mainboard AP11
If the
malfunction is
removed?
N
Y
End
N
Check connection
wire of indoor and
outdoor unit with
circuit diagram
Connection
correct?
N
N
Check connection
wire of indoor and
outdoor unit with
circuit diagram
If the malfunction
is removed?
Y
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