Carrier 40GRQB18H-3 - Communication Malfunction (AP1 below Is Control Board of Outdoor Unit)

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9. Communication malfunction (AP1 below is control board of the outdoor unit).
Main detection points:
S Check if the connection wire and the built- in wiring of the indoor and the outdoor unit is connected well and not damaged.
S Is the communication circuit of the indoor mainboard damaged? Is the communication circuit of the outdoor mainboard (AP1)
damaged?
Malfunction diagnosis process:
Start
Check communication
circuit of outdoor unit
Problem with
communication
circuit
Check built-
in wiring of
indoor and
outdoor unit
Connection
correct?
Malfunction of
circuit is
detected with
control board
AP1 voltage
Check connection
wire of indoor and
outdoor unit with
circuit diagram
Check connection
wire of indoor and
outdoor unit with
circuit diagram
If the unit is operation
normal before malfunction
Yes
N
Y
No
Is the wiring
damaged?
Does the unit operate
normally?
N
Yes
Yes
No
the unit operate
normally?
No
No
No
Replace indoor
board
Replace outdoor
mainboard AP11
If the
malfunction is
removed?
Y
No
Y
No
Y
Yes
End
Yes
Yes
Does
Fig. 45 – Troubleshooting