LG Air Conditioner Error Code E425

E425 indicates a phase reversal or phase failure on the 3-phase power supply to the LG outdoor unit. The system monitors the R-S-T-N power input and shuts down when it detects that the phase sequence is incorrect or that one or more phases are missing. This is a protective fault designed to prevent compressor damage from reverse rotation or single-phasing.

No. The unit will not operate when E425 is active because doing so could destroy the compressor within minutes. Phase reversal causes the compressor motor to run backward, and phase failure causes it to run on reduced power with extreme heat buildup. The system's automatic shutdown is a critical protection feature and should not be bypassed.

Repair costs vary depending on the root cause. If the fix only requires rewiring the phase connections at the terminal block, expect to pay for a service call plus labor, typically in the range of $150 to $350. If a fuse block, disconnect switch, or control board needs replacement, costs can range from $300 to over $800 depending on parts and local labor rates. Utility-side phase issues are typically resolved by the power company at no cost to the customer.

Diagnosing and correcting E425 involves working with 3-phase high-voltage electrical supply, which is dangerous without proper training and equipment. A licensed electrician or certified HVAC technician should check line-to-line voltages and phase rotation using a 3-phase tester before any wiring changes are made. If the issue is on the utility supply side, the technician will coordinate with the power company to resolve it.

A simple power reset will not permanently clear E425 if the underlying electrical supply problem still exists. The unit will detect the fault again on startup and re-trigger the error. The phase sequence and line voltages must be corrected first, and then the unit can be powered back on and allowed to restart normally.