LG Heat Pump Error Code E253

E253 indicates a discharge temperature sensor error on fixed capacity compressor 3. The control board has detected a sensor signal voltage either above 4.95V (open circuit, corresponding to around -30°C) or below 0.5V (short circuit, corresponding to around 151°C). This fault is only logged when the outdoor temperature is above -10°C. The system flags the error to protect the compressor from operating without valid temperature feedback.

You should not continue operating the unit with E253 active. The discharge temperature sensor protects compressor 3 from overheating, and without a valid reading the system cannot monitor compressor health. Running the heat pump under this fault condition risks compressor damage, which is a much more costly repair than resolving the sensor issue.

A power reset may temporarily clear E253, but the error will return if the underlying sensor or wiring fault is still present. Because the fault is triggered by a hard voltage threshold outside the valid sensor range, the control board will re-detect the condition as soon as normal operation resumes. A reset is useful for confirming whether the fault is intermittent, but it is not a fix and should be followed by a proper diagnostic inspection of the sensor connector and wiring.

Some steps are accessible to a knowledgeable DIYer, such as inspecting and reseating the sensor connector and visually checking the wiring harness for obvious damage. However, measuring sensor resistance accurately and safely accessing the outdoor unit components typically requires familiarity with HVAC electrical work. If the sensor or control board needs replacement, a certified HVAC technician is recommended to ensure correct parts and safe handling of the refrigerant system.

Repair costs vary depending on the root cause. Connector cleaning or reseating may involve only a service call fee, typically in the range of $75 to $150. Replacing a discharge thermistor sensor usually costs between $100 and $300 including parts and labor. If the outdoor control board is at fault, replacement costs can range from $400 to $900 or more depending on the model and labor rates in your area.