LG Heat Pump Error Code E403

E403 indicates an outdoor unit freezing detection at the third severity level, which triggers an automatic compressor shutdown to prevent damage. The system has detected that freezing conditions in the outdoor unit have exceeded safe operating thresholds. This fault points to problems with indoor airflow or refrigerant flow control, specifically the indoor fan motor and the Electronic Expansion Valve.

No, you should not attempt to force the system to continue operating when E403 is active. The control board has shut down the compressor specifically to protect it from damage caused by freezing conditions. Running the compressor under these conditions can cause liquid refrigerant to enter the compressor, resulting in costly internal damage.

Repair costs vary depending on the cause. Cleaning a dirty coil or replacing an air filter may cost very little, while an indoor fan motor replacement could range from $150 to $400 or more including labor. An EEV replacement with labor and refrigerant work can range from $300 to $700 or higher depending on the system and local labor rates. A diagnostic service call is typically the first step and can cost between $75 and $150.

Some basic checks are within reach for a knowledgeable homeowner, such as inspecting and replacing the air filter, checking that the indoor unit vents are unobstructed, and confirming the indoor fan is running. However, diagnosing or repairing the EEV, refrigerant charge, or fan motor typically requires a certified HVAC technician with proper tools and refrigerant handling credentials.

A power reset may temporarily clear the fault and allow the unit to restart, but if the underlying cause has not been resolved, the E403 code will return. Resetting without diagnosis is not a fix and repeated compressor startups under freeze conditions can accelerate wear. The root cause involving the indoor fan or EEV must be identified and corrected for the fault to stay cleared.