LG aircon CH57 error code
Use this LG CH57 error code guide to capture the fault correctly and see what should be checked before parts are quoted. Match the model first; some rows are unofficial or mean different things.
What does LG CH57 mean?
LG CH57 is listed as comms error between outdoor main PCB and inverter PCB, master outdoor unit: Outdoor inverter PCB is not receiving from the main PCB, and slave 1 outdoor unit: Outdoor inverter PCB is not receiving from the main PCB in VRF, Cassette, Ducted rows such as LG Multi V 5 commercial VRF. The loaded rows include mixed source confidence, so the model family decides which row should carry the diagnosis. Do not collapse this code across model families; use the model, series, or system type to choose the right row. Confirm the exact model, series, or signal row before accepting a parts quote.
Choose the matching source row
The same visible code has more than one source-backed meaning. Match the model family, system type, or reporting unit before approving parts.
| Code | What it means | What to check first |
|---|---|---|
| CH57 | Comms error between outdoor main PCB and inverter PCB. | Match this row to the installed model or reporting unit, then use the source-specific checks below. |
| LG Multi V 5 commercial VRF — master outdoor unit: Outdoor inverter PCB is not receiving from the main PCB | master outdoor unit: Outdoor inverter PCB is not receiving from the main PCB | Match this row to the installed model or reporting unit, then use the source-specific checks below. |
| LG Multi V 5 commercial VRF — slave 1 outdoor unit: Outdoor inverter PCB is not receiving from the main PCB | slave 1 outdoor unit: Outdoor inverter PCB is not receiving from the main PCB | Match this row to the installed model or reporting unit, then use the source-specific checks below. |
| LG Multi V 5 commercial VRF — slave 2 outdoor unit: Outdoor inverter PCB is not receiving from the main PCB | slave 2 outdoor unit: Outdoor inverter PCB is not receiving from the main PCB | Match this row to the installed model or reporting unit, then use the source-specific checks below. |
What to do now
Use these steps before customer action, a signal-wire check, or PCB quote.
Stop using the unit if CH57 returns
If CH57 remains displayed or returns during operation, do not attempt an unsourced reset; get the matching source row diagnosed.
No manufacturer reset steps listed for CH57
Capture the complete CH57 display and model stickers first. The selected source row lists no customer reset procedure; do not treat a generic power-cycle as manufacturer guidance.
Send these to us
CH57 error code, a clear display photo, LG model stickers, affected rooms, operating state when the code appeared, whether one room or every room failed, and exact model so the source can be cross-checked
Source-specific guidance
These diagnostic-reference notes help match the code to the exact model. Electrical, refrigerant, wiring, resistance, and component checks are technician work, not DIY steps.
| Source detail | What it says |
|---|---|
| Diagnostic note | Comms error between outdoor main PCB and inverter PCB. Check wiring, fuses and LEDs are lit. If OK either inverter or main PCB defective. |
| Diagnostic note | Record 571 and confirm that the master outdoor unit reported it. Have the technician trace the applicable communication wiring, plugs, addressing, and board communication path before replacing PCBs. |
| Diagnostic note | Record 572 and confirm that the slave 1 outdoor unit reported it. Have the technician trace the applicable communication wiring, plugs, addressing, and board communication path before replacing PCBs. |
| Singapore / model note | Unattributed LG fault-code list; confirm against the installed model/service manual before applying. |
| Singapore / model note | LG Singapore lists Multi V 5, but the installed unit nameplate and matching service manual control. Do not apply this row to Multi V i or another LG family. Electrical limits vary by model and supply. Use the installed Singapore supply and model data rather than thresholds from another market. |
What to check before repair
Use this split to separate safe evidence capture from the tests a technician should prove before quoting parts.
| You can check | Technician should confirm |
|---|---|
| Before taking any system action on CH57, take a clear display photo. | Match CH57 against the exact model-family source row before quoting parts. |
| Capture the LG indoor and outdoor model stickers so the correct family row is used. | Test communication terminals, cable continuity, polarity, and outdoor power. |
| The selected source row lists no customer reset procedure. Note whether one room, several rooms, or the whole system is affected. | Read indoor and outdoor PCB indicators only after the signal path is proven sound. |
Wiring or PCB decision
LG CH57 should start with terminal, signal-cable, and power checks. PCB replacement only makes sense after the communication path is proven sound.
A loose terminal or bad junction is a targeted repair once the path is confirmed.
Signal-wire replacement depends mostly on access through trunking, ceiling, or concealed routes.
PCB cost should be weighed against age only after wiring and power checks pass.
LG CH57 questions
What does the LG CH57 error mean?
Can I fix a LG CH57 error myself?
Is it safe to keep running the aircon with a CH57 error?
What causes a LG CH57 error?
Will a LG CH57 error need a repair or a full replacement?
What should I send a technician about a LG CH57 error?
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Read next
Use these if the quote mentions the parts, checks, or repair path this code points to.