Ali ElmAC Error Codes
LG air conditioners use the "CH" error code system to identify faults. When something goes wrong, a code like CH05 or CH34 appears on the indoor unit's display, the wired controller, or the LG ThinQ app. Each code points to a specific issue, from simple sensor faults through to serious compressor and refrigerant problems.
This guide covers every LG air conditioning error code across their residential split, multi-split, ducted, and Multi V (VRF) ranges. We have included what each code means in plain English, the likely cause, and whether it is something you can fix yourself or need an engineer for.
How to Find Your LG Error Code
LG units display error codes in several ways:
- Indoor unit display - The code appears directly on the LED panel of the indoor unit.
- Wired controller - On ducted and commercial systems, the error shows on the wall-mounted controller.
- LG ThinQ app - If your unit is connected to WiFi, error codes and notifications appear in the app. Download it from LG ThinQ UK.
- Outdoor unit LED - On some models, the outdoor unit's diagnostic LED flashes a code. Check the installation manual for your model's flash pattern chart.
CH Error Codes: Complete List
CH codes are the primary error code format used across all LG air conditioning ranges.
| Code | Meaning | What It Means and What to Do |
|---|---|---|
| CH01 | Indoor air temperature sensor fault | The room temperature sensor has a short or open circuit. Check the sensor connector on the indoor PCB. If the connection is good, the sensor needs replacing. |
| CH02 | Indoor pipe temperature sensor fault | The indoor coil temperature sensor has failed. Same approach as CH01, check the connector first. |
| CH03 | Drain pump error | The condensate drain pump is not working or there is a water blockage. Clean the drain line and pan first. If the pump motor has failed, it needs replacing. |
| CH04 | Indoor heat exchanger temperature sensor fault | The sensor on the indoor heat exchanger is reading outside normal range. |
| CH05 | Indoor/outdoor communication error | The indoor and outdoor units cannot communicate. Check the interconnecting cable for loose connections, damage, or incorrect wiring. This is one of the most common LG error codes. |
| CH06 | Inverter communication error | The inverter board cannot communicate with the outdoor main PCB. Internal outdoor unit fault. |
| CH07 | Outdoor unit address error | In multi-split or VRF systems, the outdoor unit address is not set correctly. Configuration issue. |
| CH09 | Indoor EEPROM error | The indoor unit's memory chip has failed or has corrupted data. Try a power reset (off at isolator for 10 minutes). If it returns, the board needs replacing. |
| CH10 | Indoor fan motor fault | The indoor fan is not running or running at incorrect speed. Check for physical obstructions in the fan barrel first. |
| CH12 | Indoor unit PCB or wired controller error | The indoor main board or wired controller has a fault. |
| CH21 | Outdoor DC compressor IPM fault | The inverter power module in the outdoor unit has failed. Requires board replacement by a qualified engineer. |
| CH22 | Outdoor CT (current transformer) error | The compressor current sensing circuit has detected an abnormality. Could indicate failing compressor or electrical fault. |
| CH23 | Outdoor DC compressor overcurrent | The compressor is drawing too much current. Possible compressor failure, low refrigerant, or short circuit. |
| CH25 | Outdoor total current overload | The system's total current draw exceeds the safe limit. May be caused by dirty coils, high ambient temperature, or compressor strain. |
| CH26 | Outdoor compressor discharge temperature high | The compressor is overheating. Usually caused by low refrigerant, dirty condenser, or a failing compressor. |
| CH27 | Outdoor pressure sensor fault | The high or low pressure sensor has failed or is reading abnormally. |
| CH32 | Outdoor heat exchanger temperature sensor fault | The outdoor coil temperature sensor has failed. |
| CH33 | Outdoor suction temperature sensor fault | The suction pipe temperature sensor has failed. |
| CH34 | High pressure switch activated | The high pressure safety switch has triggered. This indicates dangerously high refrigerant pressure. The system shuts down to protect itself. Needs immediate professional attention. |
| CH35 | Low pressure switch activated | Refrigerant pressure is too low. Likely a refrigerant leak. Needs an F-Gas certified engineer to find the leak, repair it, and recharge. |
| CH38 | Outdoor discharge temperature sensor fault | The compressor discharge temperature sensor has failed. |
| CH39 | Outdoor heat exchanger mid-point sensor fault | The mid-point sensor on the outdoor coil has failed. |
| CH40 | Outdoor defrost temperature sensor fault | The sensor that controls the defrost cycle on the outdoor coil has failed. |
| CH41 | Outdoor air temperature sensor fault | The outdoor ambient temperature sensor has failed. |
| CH44 | Outdoor unit EEPROM error | The outdoor unit's memory chip has failed. Board replacement or reprogramming needed. |
| CH45 | Outdoor condenser temperature sensor fault | The condenser coil temperature sensor has failed. |
| CH46 | Outdoor suction gas sensor fault | The suction gas temperature sensor has failed. |
| CH47 | Outdoor expansion valve fault | The electronic expansion valve is not operating correctly. |
| CH53 | Outdoor unit combination error | In multi-split or VRF systems, the outdoor unit combination is incorrect. Configuration issue. |
| CH60 | Outdoor EEPROM error (alternate) | Another outdoor memory chip fault variant. |
| CH62 | Outdoor heatsink sensor fault | The inverter heatsink temperature sensor has failed. |
| CH65 | Outdoor heatsink overheat protection | The inverter heatsink temperature is too high. Dirty outdoor coil or blocked airflow around the outdoor unit. |
| CH67 | Outdoor fan motor fault | The outdoor fan motor is not running or running abnormally. |
Other LG Error Code Formats
Some LG models use additional code formats beyond the CH system:
| Code | Meaning | What to Do |
|---|---|---|
| P2 / FL | Drain pan full | On portable and window units, the internal water collection tray is full. Empty the water via the drain plug at the back or bottom of the unit. |
| E1 | Indoor pipe temperature sensor fault | Same as CH02 on some model ranges. |
| E2 | Indoor air temperature sensor fault | Same as CH01 on some model ranges. |
| E4 | Indoor drain pump error | Same as CH03 on some model ranges. |
| E5 | Communication error | Same as CH05 on some model ranges. |
| C1 | Indoor fan motor error | Same as CH10 on some model ranges. |
| C5 | Pipe temperature sensor error | Indoor or outdoor pipe sensor fault. |
Troubleshooting Steps Before Calling an Engineer
- Power cycle - Switch off at the isolator (not the remote), wait 60 seconds, then switch back on. This clears temporary glitches from power fluctuations.
- Clean filters - Dirty filters restrict airflow and can trigger temperature sensor errors, overheating codes, and frosting. Remove, wash, dry, and refit the filters.
- Check drain (CH03 / P2 / FL) - Clear the condensate drain line. On portable units, empty the drain tray. Check the drain pump is running on ducted units.
- Check outdoor unit - Clear any leaves, debris, or objects blocking the outdoor unit. Make sure there is at least 300mm of clear space on all sides.
- Check interconnecting cable (CH05) - If you see a communication error, check the cable between indoor and outdoor units for loose connections at both ends.
When to Call a Professional
- Pressure switch codes (CH34, CH35) - High or low pressure faults involve the sealed refrigerant system. Only an F-Gas certified engineer should diagnose and repair these.
- Compressor codes (CH21, CH22, CH23, CH26) - These involve high-voltage power electronics and compressor components. Switch off at the isolator and call a qualified technician.
- Expansion valve faults (CH47) - The electronic expansion valve controls refrigerant flow and needs specialist equipment to diagnose and replace.
- Recurring codes - Any error that returns after a power cycle indicates a genuine hardware fault that needs professional diagnosis.
UK Regulations for LG AC Systems
- F-Gas Regulation - LG systems using R32 or R410A refrigerant require regular leak checks by F-Gas certified engineers. Frequency depends on the CO2 equivalent charge. See the UK Government F-Gas guidance.
- TM44 Inspections - AC systems over 12kW combined cooling capacity must be inspected every five years. See UK Government air conditioning inspections.
Official LG Resources
- LG UK Business Air Conditioning - Commercial product range, technical specs, and support.
- LG ThinQ UK - Smart monitoring app for error notifications and remote control.
- LG UK Support - Manuals, warranty information, and service contacts.
Written by
Ali Elm
Ali is the Head of Operations at Be Cool Refrigeration with over a decade of hands-on experience in HVAC and commercial refrigeration. He oversees every installation, repair, and maintenance project, making sure the work meets the highest standards. Ali holds full F-Gas certification and has worked across residential, commercial, and industrial refrigeration systems throughout London and the South East. When he is not on site, he writes these guides to help business owners and homeowners understand their cooling systems better.