LG Air Conditioner Error Code E404

E404 indicates an outdoor unit heating overload condition that has triggered the compressor safety shutdown. The system detected that the compressor was operating beyond safe pressure or thermal limits during heating mode. This is a protective fault designed to prevent compressor damage. The most common causes are restricted airflow at the indoor or outdoor unit, or refrigerant overcharge.

Resetting the unit by cycling power may temporarily clear the E404 fault and allow the compressor to restart, but the error will return if the underlying cause is not resolved. The overload protection is designed to reactivate whenever the fault condition is present. Clearing the code without fixing the root cause risks repeated compressor shutdowns and potential long-term compressor damage.

Repair costs depend entirely on the root cause. Clearing a blocked outdoor unit or replacing air filters may cost little to nothing if done yourself. A service call for refrigerant diagnosis and correction typically ranges from $150 to $400 depending on the amount of refrigerant involved and local labor rates. If a pressure switch or sensor needs replacement, parts and labor combined generally range from $200 to $500.

Some causes of E404 can be addressed without a technician, such as cleaning or replacing dirty indoor air filters, clearing snow or debris from the outdoor unit, and verifying that nothing is blocking the outdoor coil or fan. However, if the cause is refrigerant overcharge or a faulty pressure switch, a licensed HVAC technician is required to handle refrigerants and perform accurate pressure diagnostics.

The E404 fault itself is a safety feature, meaning the system is doing its job by stopping the compressor before a more serious failure occurs. Running the unit repeatedly through reset cycles without addressing the cause can stress the compressor and shorten its lifespan. You should identify and correct the airflow or refrigerant issue before returning the unit to regular operation.