LG Heat Pump Error Code E451

E451 indicates that the outdoor unit discharge temperature sensor 1 has detected an excessively high temperature at the compressor discharge line, triggering a protection control response. The system activates this protection to prevent compressor damage from overheating. Common causes include low refrigerant, blocked outdoor coil, a failed fan motor, or a faulty sensor.

No, you should not continue operating the heat pump while the E451 error is active. The protection control is designed to shut the system down to prevent compressor damage. Running the system in a faulted condition can cause permanent and costly compressor failure.

Repair costs vary widely depending on the cause. A coil cleaning or sensor replacement may cost in the range of $100 to $300, while refrigerant leak detection, repair, and recharge can range from $250 to $600 or more. A compressor replacement, if the unit has already sustained damage, can run from $800 to $2,000 or higher depending on the unit size and labor rates in your area.

Some basic checks, like clearing debris from the outdoor coil and confirming the outdoor fan is spinning, can be done by a homeowner. However, diagnosing refrigerant charge issues, testing the discharge temperature sensor, or replacing components requires a licensed HVAC technician with proper tools and certifications. Attempting refrigerant work without certification is illegal and unsafe.

A reset may temporarily clear the error code, but if the underlying cause is not resolved, the fault will return, often quickly. Simply resetting the unit without diagnosing and correcting the root cause risks further damage to the compressor and other components. A proper diagnostic inspection should be completed before restarting the system.