LG Air Conditioner Error Code 73

Error code 73 on an LG air conditioner indicates a PFC fault caused by an instantaneous overcurrent on the AC input to the inverter PCB. The system has detected current exceeding 48 amperes peak for at least 2 milliseconds and has shut down to protect the board and compressor. This can be triggered by refrigerant issues, a faulty EEV, piping restrictions, out-of-range supply voltage, or poor wiring connections at the compressor.

The error itself is a protective shutdown, meaning the unit has already stopped operating to prevent further damage. However, the underlying conditions that caused it, such as a wiring fault or a heavily overloaded compressor, can pose risks if ignored. Do not repeatedly attempt to restart the unit without diagnosing the root cause, as continued operation under overcurrent conditions can damage the inverter PCB or compressor.

Repair costs vary widely depending on what is causing the fault. If the issue is simply a wiring connection or a covered outdoor unit, costs may be limited to a service call fee, typically in the range of $75 to $150. If the EEV needs replacement or refrigerant must be recovered and recharged, costs can range from $200 to $600 or more. Inverter PCB replacement, if the board has been damaged, can push total repair costs into the $400 to $900 range depending on parts and labor in your area.

Some preliminary checks, such as confirming the outdoor unit is not obstructed or covered and inspecting visible wiring for obvious damage, can be done without special tools. However, checking refrigerant pressures, testing the EEV, and measuring AC input voltage under load require proper equipment and training. Because this fault involves high-voltage inverter circuitry and refrigerant handling, most of the diagnostic and repair work should be performed by a qualified technician.

A power cycle may temporarily clear the fault and allow the unit to restart, but if the underlying cause is not resolved, the error code 73 will return, often quickly. Repeatedly resetting without fixing the root cause risks permanent damage to the inverter PCB. A full diagnostic check of refrigerant pressures, EEV operation, input voltage, and wiring should be completed before relying on a reset.