LG Air Conditioner Error Code 155

Error code 155 indicates that the sub3 outdoor unit in your LG system has detected a problem with its 3-phase power supply. The fault is specifically a reverse phase condition (wrong wire sequence) or a phase omission (one phase is missing). The system shuts down to prevent damage to the compressor and fan motors, which rely on correct phase order to rotate in the right direction.

No. The system is designed to shut down when error 155 is detected to prevent damage. Operating a 3-phase compressor with a reversed phase or missing phase can cause the motor to run backwards or not run at all, which can result in serious mechanical damage to the compressor and other components. Do not attempt to bypass this fault and leave the unit off until the power supply issue is resolved.

If the fix is correcting swapped wires or tightening a loose terminal, the cost is primarily the service call fee, which typically ranges from $75 to $200 depending on your location and the technician's rates. If a breaker or fuse needs replacement, parts are generally inexpensive, adding $20 to $100. In the rare case where the phase detection board or main PCB is faulty and needs replacement, costs can increase significantly, ranging from $300 to $800 or more depending on parts and labor.

Diagnosing and correcting 3-phase wiring issues involves working with high-voltage commercial electrical systems, which is dangerous without proper training and equipment. A licensed electrician or certified HVAC technician should inspect the phase order and confirm all three phases are present using a phase rotation meter and multimeter. If the issue is simply two swapped wires at the terminal block, the fix is straightforward once the problem is identified, but the work itself should be performed by a qualified professional.

A simple reset will not permanently clear error code 155 because the phase detection circuit will re-evaluate the incoming power each time the unit starts. If the underlying wiring issue has not been corrected, the fault code will return immediately upon restart. The error will only clear and stay cleared once the phase sequence is correct and all three phases are present and stable at the sub3 outdoor unit.