LG Heat Pump Error Code E103

E103 indicates that the indoor unit's evaporator inlet temperature sensor has been detected in an open or short circuit condition. The sensor is an NTC thermistor that monitors refrigerant temperature entering the indoor coil. When its resistance signal falls outside the expected range, the PCB triggers this fault and halts normal operation. The issue can be in the sensor itself, the wiring, or the PCB.

The heat pump will typically suspend normal operation when E103 is active, so the system is protecting itself from running without accurate temperature data. Attempting to bypass or ignore this fault is not recommended, as the evaporator inlet sensor is used for freeze protection and refrigerant management. You should resolve the fault before returning the unit to regular use.

If only the EVAP IN thermistor needs replacement, parts typically cost between $15 and $60 depending on the specific model, with labor adding $75 to $200 if a technician is involved. If the indoor PCB is the root cause, costs rise considerably, with PCB parts ranging from $100 to $400 or more and additional labor on top of that. Getting a diagnostic visit from a technician first can help narrow the repair cost before committing to parts.

A knowledgeable DIYer can check the sensor connector for loose or corroded connections, which requires no special tools. To properly diagnose the fault, you will need a multimeter to measure sensor resistance and a resistance-temperature table for the specific sensor. Replacing the thermistor is a straightforward repair if that is confirmed as the cause. However, if the indoor PCB is at fault, replacement is more involved and may be better handled by a qualified technician.

A power reset may temporarily clear the fault display, but if the underlying sensor or wiring problem still exists, the E103 code will return once the PCB re-evaluates the sensor signal. A reset alone is not a fix. The sensor circuit must be inspected and repaired before the error will stay cleared.