LG MULTI V M ARNU07GTU 4 Series Svc Manual page 76

Troubleshooting Guide
Error
Error Type
No.
Communication error
between
521
(Inv. PCB ' Main PCB)
n Error diagnosis and countermeasure flow chart
Is the heat exchanger
module turned on?
Yes
Is communication
LED (Yellow) of
Inv. PCB on?
Yes
Is communication cable
connected correctly?
Yes
Is Main PCB normal?
Yes
Replace Inv. PCB
* The method of checking Main PCB and Inv. PCB (If normal, communication LED blinks)
Error Point
Main PCB of Master unit
of Master unit can't
receive signal from Inv.
PCB
No
Turn on the heat exchanger module.
No
Re-connect communication cable
No
Re-connect communication cable
No
Replace Main PCB
Inverter Communication LED
1. Power cable or communication cable is not
connected
2. Defect of outdoor Main PCB or Inv. PCB
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Main Reasons
Inverter Communication
Connector