LG Heat Pump Error Code E324

E324 indicates a fault with the SUMP TEMP FIXED 3 temperature sensor in the heat pump system. The control board has detected that the sensor's signal voltage is either above 4.95V (corresponding to a reading below -30 degrees Celsius, suggesting an open circuit) or below 0.5V (corresponding to a reading above 151 degrees Celsius, suggesting a short circuit). This fault is only triggered when outdoor temperatures are above -10 degrees Celsius, ensuring the detection is not a cold-weather false positive.

The heat pump will generally shut down or restrict operation when E324 is active, as the control system cannot reliably monitor sump temperatures without a valid sensor signal. Continuing to operate the unit while this fault is present could risk undetected temperature extremes within the refrigerant circuit. It is advisable to leave the unit off until the fault is diagnosed and resolved.

Repair costs depend on the root cause. If only a connector needs cleaning or reseating, the cost may be limited to a service call fee, typically in the range of 75 to 150 dollars. Replacing the SUMP TEMP FIXED 3 sensor itself generally costs between 50 and 150 dollars for the part plus labor. If the control board has failed and requires replacement, total costs including parts and labor can range from 400 to 900 dollars or more depending on the model.

Some causes of E324 are accessible to a knowledgeable DIYer, such as inspecting and reseating wiring connectors or checking for obvious damage to the sensor harness. However, confirming whether the sensor or control board has failed requires a multimeter to test sensor resistance and circuit voltage, which demands familiarity with electrical diagnostics. Refrigerant system work is not typically involved with this sensor fault, but working inside an outdoor unit still carries electrical hazard risks, so caution is essential.

A power cycle reset may temporarily clear the displayed error, but if the underlying sensor or wiring fault still exists, the code will return once the system restarts and the outdoor temperature is above -10 degrees Celsius. A reset alone does not repair a faulty sensor, damaged wiring, or corroded connector. The root cause must be identified and corrected for the error to stay cleared.