LG ARWN038GA2 Service Manual page 76

Troubleshooting Guide
Error No. Error Type
74*
Power Unbalance
■ Error Diagnosis and Countermeasure Flow Chart
Is inverter PCB assembly
power wiring normal?
Yes
Is input voltage normal?
Yes
Does indoor unit power
bridge R,S,T phase equally?
Yes
Is inverter PCB
assembly normal?
Yes
Recheck power and
installing condition
Measuring input voltage
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Error Point
During operation (compressor fre-
quency is over 50Hz), difference
between R & T phase is 5A for 10
seconds.
No
Check abnormal wiring between Inverter PCB assembly & bridge diode
(misconnection,disconnection)
→ Rewiring if abnormal wiring found
Check
No
R~S/S~T/T~R phase voltage is 380V 10%
R~N/S~N/T~N phase voltage is 220V 10%
→ Check connection condition and wiring if power is abnormal
No
Bridge R-N,S-N,T-N voltage equally
No
Replace inverter PCB assembly
Inverter PCB & Bridge Diode wiring
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Main Reasons
1. CT sensor defect
2. Capacity over of AVR
3. Bridge R-N or S-N or T-N phase
voltage unequally at indoor unit
etc.
LGE Internal Use Only