LG Heat Pump Error Code E284

E284 indicates a fault with the SUMP TEMP FIXED 3 sensor in the outdoor unit. The control board has detected a signal voltage either above 4.95V (open circuit, reading below -30°C) or below 0.5V (short circuit, reading above 151°C), both of which are outside the valid operating range. The error is only triggered when outdoor ambient temperature is above -10°C. The root cause is typically a disconnected connector, a failed sensor, or damaged wiring.

The heat pump will typically stop normal operation when E284 is active because the sump temperature data is needed for safe system management. Attempting to force the unit to run without a valid sensor reading could result in inadequate protection of compressor components. It is best to leave the unit off until the sensor fault is resolved.

A power reset may temporarily clear the error code from the display, but the fault will return as soon as the system restarts and the control board detects the same out-of-range voltage on the sensor input. Because E284 reflects an actual hardware problem with the sensor circuit, the underlying issue must be diagnosed and repaired before the error will stay cleared permanently.

Some basic checks are within reach for a knowledgeable DIYer, including inspecting the sensor connector for a loose fit or visible corrosion and reseating it firmly. However, measuring sensor resistance and comparing it to the resistance-temperature specification table requires a multimeter and some familiarity with how NTC thermistors behave. Replacing a sensor or diagnosing a control board fault is generally better handled by a certified technician.

If the fix is as simple as reseating a loose connector, there may be no parts cost at all, just a service call fee that typically ranges from $75 to $150 depending on your area. Replacing a faulty sump temperature sensor usually costs between $20 and $80 for the part, plus labor. If the main control board is the cause, board replacement can range from $200 to $600 or more depending on the model.