LG Air Conditioner Error Code 78

Error code 78 on an LG air conditioner indicates a hall sensor fault in the fan motor. The hall sensor monitors fan rotor position and speed, and the code is triggered when the sensor circuit reads as open or shorted. This prevents the PCB from controlling the fan motor and causes the unit to shut down. The fault points to either a wiring or connector issue, or a failed fan motor assembly.

No, you should not continue running the unit with error code 78 active. The error means the PCB has lost reliable feedback from the fan motor, which prevents safe speed control of the fan. Running the system in this state could cause the motor to overheat or result in further damage to the control board or other components.

A power reset may temporarily clear the error display, but the code will return as soon as the unit powers on and the PCB detects the same open or short condition in the hall sensor circuit. Error code 78 reflects an active electrical fault that requires physical diagnosis and repair, not just a reset. The underlying wiring or motor problem must be resolved before the unit will operate normally.

Some causes of error code 78 are accessible to a knowledgeable DIYer. You can inspect and reseat the hall sensor connector, verify wire color matching between the motor harness and PCB connector, and look for visible wiring damage. However, if the fault is inside the fan motor assembly itself, replacing the motor requires disassembly of the unit and working around capacitors that can store a dangerous charge, so professional service is recommended for that repair.

If the repair only requires reseating or replacing a connector or harness, costs are typically in the range of $75 to $150 for a service call and minor parts. If the fan motor assembly has failed and needs replacement, total repair costs including labor can range from $200 to $450 or more depending on the model and local labor rates.