LG Hvac Error Code 47

Error code 47 on an LG HVAC system indicates that the outdoor unit (ODU) PCB has detected a fault with the single-speed compressor discharge pipe thermistor. This thermistor monitors the temperature of the refrigerant discharge line exiting the compressor, which is a critical measurement for protecting the compressor from overheating conditions. The PCB continuously checks the signal from this sensor, and when the resistance reading falls outside the expected range, it flags the circuit as either open (broken circuit, infinite resistance) or shorted (near-zero resistance), triggering the error.

The thermistor for this application follows a standard NTC (negative temperature coefficient) curve with a specified resistance of 244,000 ohms at 20 degrees Celsius (68 degrees Fahrenheit) and 24,400 ohms at 90 degrees Celsius (194 degrees Fahrenheit). These reference values are the key benchmarks for diagnosis. To properly evaluate the sensor, it should be tested by submerging it in water at a known temperature and measuring resistance with a multimeter. If the readings match the specification, the sensor is functioning correctly and the fault is more likely a wiring or connector issue, or in confirmed cases of good wiring and a good thermistor, a failed PCB.

Common failure points include thermistor degradation from prolonged heat exposure near the discharge line, connector corrosion or pin damage causing intermittent open circuits, and damaged wiring insulation leading to shorts. Because the discharge pipe operates at high temperatures during normal system operation, the thermistor and its harness are exposed to thermal stress over time. Always rule out the sensor and wiring before replacing the PCB, as PCB replacement is significantly more costly.