LG Air Conditioner Error Code 218

Error code 218 on an LG air conditioner indicates a sub-cooling inlet pipe temperature sensor error on HR unit 5. The system has detected that the thermistor circuit is either open (broken) or shorted, producing an implausible temperature reading. This is a fault specific to multi-zone heat recovery systems that use dedicated HR units. The system flags this to protect refrigerant circuit operation.

Running the system with an active sensor error is not recommended. The sub-cooling inlet temperature sensor provides data the control system uses to manage refrigerant flow in the HR unit. Operating without accurate sensor feedback can lead to improper refrigerant management and potential damage to system components over time.

A power reset may temporarily clear the error code, but if the underlying sensor or wiring fault is still present, the code will return once the system restarts and checks the sensor input. A reset is useful for confirming whether the fault is intermittent, but it does not address the root cause. The sensor connection and lead cable should be inspected before relying on a reset as a solution.

Basic checks such as inspecting the sensor connector for looseness or visible damage to the lead cable can be performed by a knowledgeable DIYer. However, resistance testing the thermistor and tracing wiring faults through a heat recovery unit typically requires familiarity with refrigerant system components and electrical testing. If the sensor or wiring needs replacement, a qualified HVAC technician is recommended.

If the fix is simply reseating a loose connector, there may be no parts cost, only a service call fee which typically ranges from $75 to $150 depending on your area. If the thermistor sensor or lead cable needs replacement, parts and labor combined could range from $150 to $400 or more depending on part availability and system accessibility.