LG Air Conditioner Error Code E407

E407 means the system's high pressure sensor detected refrigerant pressure at or above 40 kg/cm2, which triggered an automatic compressor shutdown to prevent damage. This is a high pressure protection fault, meaning the refrigerant circuit is operating above safe limits. The unit will not restart until the underlying cause is identified and corrected.

No. The E407 fault shuts the compressor down specifically to prevent damage from dangerously high refrigerant pressure. Attempting to bypass or repeatedly reset the fault without resolving the root cause risks compressor failure, refrigerant line damage, or other costly component failures. The system should remain off until a qualified technician diagnoses and corrects the issue.

Repair costs vary widely depending on the root cause. Simple fixes like opening a closed service valve may cost only a diagnostic fee, typically in the range of $75 to $150. Replacing an EEV or outdoor fan motor can range from $200 to $600 or more depending on parts and labor rates. If the compressor sustained damage from repeated high pressure events, replacement costs can be significantly higher.

Some basic checks, such as confirming the outdoor unit has clear airflow and verifying the service valves are fully open, can be done without special tools. However, diagnosing EEV operation, checking refrigerant charge, and reading live sensor data requires S-net diagnostic software and manifold gauges, which are professional tools. A licensed HVAC technician should be involved for any steps beyond visual inspection.

A power reset may temporarily clear the fault and allow the unit to restart, but E407 will return if the underlying cause, such as a failed outdoor fan, restricted EEV, or closed service valve, has not been addressed. Repeated resets without fixing the root cause can lead to progressive compressor damage. A reset should only be used after a physical inspection confirms the system is safe to operate.