LG HVAC Error Code 57

Error code 57 indicates a communication failure between the outdoor unit's main PCB and its inverter PCB. These two boards must exchange data continuously to control compressor operation, and when that link breaks down the system faults out and shuts off. The cause can range from a loose wire or blown fuse to a fully failed circuit board.

A power reset may temporarily clear the fault display, but if the underlying wiring fault or PCB failure is still present the error will return as soon as the system attempts to restart and the boards try to communicate. A reset is useful for confirming whether the fault is intermittent, but it does not fix the root cause. Persistent or recurring error 57 requires physical inspection and component testing.

Repair cost depends on what component has failed. If the fix is a loose connector or a fuse, parts cost is minimal and labor may be one to two hours. If the inverter PCB or main PCB needs replacement, parts alone typically range from $150 to $600 or more depending on the model, plus labor. Getting a diagnosis from a certified technician before purchasing parts is the best way to avoid unnecessary expense.

A knowledgeable DIYer can safely check for obvious wiring issues and inspect fuses in the outdoor unit, but working inside the outdoor unit on inverter components involves high-voltage DC bus capacitors that can hold a dangerous charge even after power is disconnected. If basic wiring checks do not resolve the error, PCB diagnosis and replacement should be handled by a qualified technician. Attempting to swap inverter or main PCBs without proper training carries a serious shock risk.

No. When error code 57 is active, the system has already shut down the compressor because safe coordinated control is not possible without communication between the two PCBs. Attempting to force the unit to operate in this state is not recommended and could cause further damage to the inverter or compressor. Leave the unit off until the fault is diagnosed and repaired.