LG aircon CH90 / CH91 error code
Use this LG CH90 / CH91 error code guide to capture the fault correctly and see what should be checked before parts are quoted.
What does LG CH90 / CH91 mean?
LG CH90 / CH91 is listed as test-run piping connection issue in Inverter Split, Multi-Split rows. The loaded row is source-backed by official diagnostic material. Confirm the exact model, series, or signal row before accepting a parts quote.
Indoor and outdoor unit capacity, jumper, model, or platform mismatch.
Incorrect setting after installation, PCB change, or mixed-system work.
Communication or board configuration issue if the setting is correct but the fault returns.
What to do now
Use these steps before customer action or a parts quote.
Stop using the unit if CH90 / CH91 returns
If CH90 / CH91 remains displayed or returns during operation, do not attempt an unsourced reset; get the matching source row diagnosed.
No manufacturer reset steps listed for CH90 / CH91
Capture the complete CH90 / CH91 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
CH90 / CH91 error code, a clear display photo, LG model stickers, affected rooms, operating state when the code appeared, and recent installation, PCB, or model-pairing work
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 | Test-run piping connection issue. If it appears after installation or relocation, check refrigerant pipe connection and commissioning state before handover. |
| Singapore / model note | Official LG help-library guide; useful for post-installation callbacks where a new system fails during commissioning. |
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 CH90 / CH91, take a clear display photo. | Confirm the exact model pairing behind CH90 / CH91. |
| Capture the LG indoor and outdoor model stickers so the correct family row is used. | Check jumper caps, capacity settings, paired indoor/outdoor model compatibility, and recent board changes. |
| The selected source row lists no customer reset procedure. Note whether one room, several rooms, or the whole system is affected. | Only quote parts after configuration and communication checks are ruled out. |
What changes the next step
These clues decide whether the first check is room-side, shared outdoor-side, refrigerant-side, source-table, or model-family confirmation.
| What you see | What it points to |
|---|---|
| Only one indoor unit shows CH90 / CH91. | The affected room, indoor board path, wiring route, or local component should be checked first. |
| Several rooms or the outdoor unit show the same CH90 / CH91 fault. | Prioritise the shared outdoor side, power path, and source-listed system branch. |
| The fault remains displayed or returns during operation. | Start with the source-row diagnostic branch before approving parts. |
| The model family is different from the row you found online. | Use the model or series filter first; same-looking codes can still belong to different diagnostic tables. |
| The model belongs to Inverter Split, Multi-Split rows. | The loaded row is source-backed by official diagnostic material. Use the matching source row before quoting parts. |
Configuration or parts decision
LG CH90 / CH91 can often be corrected by matching settings, model pairing, or board configuration. Parts should be quoted only after setup is confirmed.
Wrong capacity or pairing settings can mimic a hardware fault.
Recent installation, PCB replacement, or mixed-model work changes the first check.
Once configuration is confirmed, the diagnosis can move to wiring or board inputs.
LG CH90 / CH91 questions
What does the LG CH90 / CH91 error mean?
Can I fix a LG CH90 / CH91 error myself?
Is it safe to keep running the aircon with a CH90 / CH91 error?
What causes a LG CH90 / CH91 error?
Will a LG CH90 / CH91 error need a repair or a full replacement?
What should I send a technician about a LG CH90 / CH91 error?
Confirm the fault
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Read next
Use these if the quote mentions the parts, checks, or repair path this code points to.