LG AMNW07GDBL1 Service Manual page 77

Part 5. Trouble Shooting
► A4UW36GFA0/A8UW54GFA0
Display
Title
code
21 DC PEAK
(IPM Fault)
WARNING
Before checking PCB or each outdoor electric parts, wait for 3 minutes after the power is off. When measuring at standby state
of power supply, after checking the measurement mode of the meter, be careful of the short-circuits with other parts.
■ Error Diagnosis and Countermeasure Flow Chart
Is installation
condition normal?
Yes
Are the resistance
Between each phase and
insulation resistance of Inverter
compressor normal?
Yes
Is compressor
Wire connection
condition normal?
Yes
Is inverter PCB assembly normal?
Yes
Recheck power and installation condition
■ Comp checking method
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Only for training and service purposes
Cause of error
• Instant over current
• Over Rated current
• Poor insulation of IPM
1. Check Pipe clogging/distortion
2. Check Covering (Indoor/Outdoor Unit)
3. Check EEV connector assemble condition/normal
No
operation
4. Check refrigerant pressure
→ Reassemble or manage if abnormality found
1. Check resistance between each terminal of compressor
(0.438~0.628±7%)
No
2. Check insulation resistance between compressor
terminal and pipe (over 2MΩ)
→ Replace compressor if abnormality found
1. Check inverter PCB assembly U,V,W connector
connection condition
2. Check wire disconnection and wiring
No
3. Check compressor terminal connection condition
(bad contact)
→ Reassemble if abnormality found
Check inverter PCB assembly IPM normality
No
→ Replace inverter PCB assembly
Comp
U
V W
Copper
Comp
pipe
- 76 -
Check point & Normal condition
• An instant over current in the U,V,W phase
- Comp lock
- The abnormal connection of U,V,W
• Over load condition
- Overcharging of refrigerant Pipe length.
Outdoor Fan is stop
• Poor insulation of compressor
Resistance(Ω)
Model
Terminal
U-V
36k
V-W
W-U
U-V
54k
V-W
W-U
Resistance(Ω) at 20°C
Inverter
Terminal
comp.
U-GND 2MΩ
V-GND 2MΩ
W-GND 2MΩ
Inverter Comp.
0.628(at 25˚C)
0.628(at 25˚C)
0.628(at 25˚C)
0.438(at 25˚C)
0.438(at 25˚C)
0.438(at 25˚C)
Constant
comp.
2MΩ
2MΩ
2MΩ
LGE Internal Use Only