LG Air Conditioner Error Code 4

Error code 4 on an LG air conditioner means the heat sink on the power module (inverter drive module) in the outdoor unit has reached or exceeded 95°C, triggering overheating protection. The compressor shuts down to prevent damage and will restart automatically once the heat sink cools below 85°C. The fault points to a thermal management problem such as restricted airflow, a dirty condenser coil, or a failing outdoor fan motor.

The unit is protecting itself by shutting down when error code 4 appears, so you are not in immediate danger. However, continuing to operate the system without fixing the cause of the overheating risks permanent damage to the inverter power module, which is one of the most expensive components in the outdoor unit. It is best to address the problem before regular use resumes.

Cycling power to the unit will clear the displayed error code and allow the system to restart once the heat sink has cooled below 85°C. However, resetting does not fix the underlying problem. If the cause of the overheating is not corrected, such as a blocked coil, restricted airflow, or a failing fan motor, the error will return and the system will shut down again.

Yes, the system is designed to restart automatically once the heat sink thermistor temperature drops below 85°C. However, if the underlying cause of the overheating is not corrected, the fault will trigger again shortly after restart. Repeated cycling through this fault can cause long-term damage to the power module, so the root cause should be diagnosed and resolved.

Repair costs vary widely depending on the cause. Cleaning the condenser coil or clearing airflow obstructions may cost between $75 and $200 for a service call. Replacing a failed outdoor fan motor typically runs between $150 and $400 including parts and labor. If the power module itself has been damaged by repeated overheating, replacement costs can range from $300 to $700 or more depending on the model.