LG HVAC Error Code 45

Error code 45 means the outdoor unit's PCB is detecting an open or shorted circuit in the condenser coil thermistor, specifically the sensor located at the middle or exit (liquid line) position of the condenser coil. The board cannot get a valid temperature reading from that sensor. This will typically prevent normal operation to protect the system from running without accurate coil temperature data.

Running the system while ignoring this fault can lead to unmonitored condenser coil temperatures, which may allow the system to operate outside safe parameters. Over time this could cause refrigerant or compressor damage. It is advisable to diagnose and resolve the fault before continuing regular operation.

A power reset may temporarily clear the error from the display, but the code will return as soon as the PCB polls the thermistor circuit and detects the same open or short condition again. Resetting does not address the underlying hardware fault. A proper repair of the thermistor, wiring, or PCB is required for the code to clear permanently.

A knowledgeable DIYer can perform the initial diagnostic by disconnecting the thermistor, submerging it in water at a known temperature, and measuring resistance with a multimeter against the reference values of 2,800 ohms at 38°C and 10,000 ohms at 10°C. Replacing the thermistor is also a relatively straightforward repair. However, if the fault points to the PCB, replacement of that component involves working inside the outdoor unit's electrical panel, which is best handled by a certified HVAC technician.

If the thermistor itself is the cause, parts typically cost in the range of $20 to $80 depending on the specific model, with labor adding $75 to $150 if a technician performs the work. If the PCB is at fault, board replacement is significantly more expensive, generally ranging from $200 to $600 or more for parts and labor combined.