LG Aircon Error Codes and Blinking Light Guide

Most LG wall-mounted units in Singapore (Alpha and Artcool+ series) have two LEDs on the front panel. The power or operation LED (green on most models, yellow-green when running on post-2014 units) shows running status. A secondary LED handles timer, sleep, and filter cleaning reminders.

On units with a digital display or wired remote, error codes appear directly as CH followed by a two-digit number. On LED-only units without a display, the two LEDs encode the error code through counted blinks — the power LED blinks for the units digit and the secondary LED blinks for the tens digit. Two blinks on the power LED plus one blink on the secondary LED means CH21.

The outdoor unit PCB has its own pair of diagnostic LEDs. A steady green LED means the board has power. A flickering red LED means the board is receiving communication from the indoor unit. A steady (non-flickering) red LED means communication has stopped. No red light at all points to an outdoor PCB fault.

A steady green or yellow-green LED during operation is normal. On post-2014 models, the LED turns yellow when the unit is in standby (powered but not running). Older models keep the green LED lit even when the unit is off — this is not a fault.

The filter indicator lights up after roughly 2,400 hours of cumulative operation. It is a maintenance reminder, not an error. Clean the filter, then press the Cancel Reservation or Set/Release button on the remote three times to reset it.

During heating mode, an E4 display or brief LED blink can indicate a defrost cycle. The unit pauses to deice the outdoor coil and resumes automatically. This is uncommon in Singapore unless the outdoor coil is heavily soiled or the unit is running in dry mode for extended periods.

When a fault occurs, LG units display a CH code followed by a two-digit number. On display-equipped models, the code shows directly on the panel or wired remote. On LED-only models, count the blinks on each LED — the power LED gives the units digit and the secondary LED gives the tens digit, with a pause between each sequence.

If multiple faults occur at the same time, the lowest-numbered code displays first. After that fault is resolved, the next code appears. To reset after resolving the issue, turn off the unit at the circuit breaker, wait five minutes, and restore power. If the code returns, the underlying fault persists.

For the outdoor unit PCB, the red LED (LED01G) blinks for the tens digit and the green LED (LED02G) blinks for the units digit. This requires opening the outdoor unit cover, so it is mainly useful for technicians during on-site diagnosis.

CH01 through CH12 cover indoor unit sensors and communication faults. CH05 (communication error between indoor and outdoor units) is the most common code in Singapore homes, especially after power surges or lightning events. A five-minute power reset at the breaker often clears it. If CH05 returns, the issue is typically a loose interconnecting cable or a faulty PCB.

CH02 (indoor air temperature sensor) and CH01 (indoor pipe sensor) are straightforward sensor faults — the thermistor is defective or its connector is loose. CH10 (indoor fan motor error) and CH08 (fan not rotating) require checking for physical obstructions before calling a technician.

CH09 (EEPROM failure) means the indoor control board's memory is corrupted. A power cycle sometimes clears it, but if it recurs, the PCB needs replacement.

CH21 through CH38 are serious codes covering the compressor, inverter, and refrigerant circuit. CH21 (compressor locked or overloaded) and CH22 (inverter overcurrent) both require immediate power-off. Do not restart the unit until a technician has inspected it.

CH24 (high or low pressure trip) and CH38 (low refrigerant) often indicate a refrigerant leak. CH32 and CH33 (high discharge temperature) can sometimes be addressed by cleaning filters and the outdoor condenser coil. If the code returns after cleaning, the system likely needs a gas check.

CH25 (abnormal power supply voltage) is not an aircon fault — it means the mains voltage is outside the acceptable range. An electrician should check the supply before the aircon technician is called.

LG multi-split systems (System 2, 3, and 4) are common in Singapore HDB and condo installations, particularly the Alpha and Artcool+ lines. When the outdoor unit faults, all connected indoor units display the same error code because they share the same communication and refrigerant circuit.

CH07 (mode conflict) is exclusive to multi-split setups — it appears when one indoor unit is set to cooling while another requests a different mode. All units must operate in the same mode. CH51 (unit mismatch) means the connected indoor units exceed the outdoor unit's capacity or are incompatible models.

For any CH21-series code (compressor, inverter, overcurrent), turn off the unit and call a technician. For CH05 or CH53 (communication errors), try a five-minute power reset first. For CH61 (indoor temperature too high), clean the filters thoroughly — this is the most common self-fixable code. If any code returns after your initial troubleshooting, professional diagnosis is the next step.