LG Heat Pump Error Code P743

P743 indicates that outdoor unit discharge temperature sensor 3 has detected a temperature above the safe operating limit, triggering a protection control shutdown. The discharge temperature is measured at the compressor outlet, which is one of the hottest points in the refrigerant circuit. The system stops operation automatically to prevent compressor damage. A full diagnostic is needed to identify why discharge temperatures reached a protection level.

No. The P743 protection control shuts down the unit specifically to prevent compressor damage from excessive heat. Bypassing or repeatedly resetting the fault without addressing the root cause risks permanent compressor failure, which is the most expensive component in the system. Leave the unit off until a technician has diagnosed and corrected the underlying issue.

Repair costs vary widely depending on the cause. A condenser coil cleaning or sensor replacement may cost between $100 and $300. Refrigerant leak detection, repair, and recharge can range from $200 to $600 or more. If the compressor has been damaged by sustained high discharge temperatures, replacement costs can range from $1,200 to $2,500 or higher depending on the unit. Early diagnosis is the best way to keep repair costs manageable.

Some basic checks are possible without professional tools, such as inspecting the outdoor unit for debris blocking the condenser coil or confirming the outdoor fan is running. However, diagnosing the root cause typically requires refrigerant pressure gauges, a multimeter to test sensor resistance, and knowledge of the refrigeration circuit. Because refrigerant handling requires EPA certification, most repairs should be handled by a licensed HVAC technician.

A power reset may temporarily clear the fault and allow the unit to restart, but the code will return if the underlying cause has not been corrected. Repeated faults in the same session may cause the system to lock out more aggressively. Resetting without diagnosis is not a fix and delays proper repair while increasing the risk of compressor damage.