LG HVAC Error Code 1

Error code 1 on an LG HVAC system means the control board has detected that the indoor unit pipe thermistor or air thermistor is reading as open or shorted. This applies to Inverter, 10/13 SEER, and PTAC unit types. The system cannot accurately monitor temperatures without a functioning thermistor, so it generates this fault code and may stop operating normally. A technician will test the thermistor's resistance against known specification values to determine whether the sensor, wiring, or PCB is at fault.

Continuing to operate the unit with error code 1 active is not recommended. Without a functioning thermistor, the PCB cannot accurately monitor refrigerant line or air temperatures, which can lead to issues such as coil freeze-up, compressor damage, or improper cooling and heating cycles. The system may shut itself down automatically as a protective measure.

Repair costs depend on which component has failed. A replacement thermistor is typically an inexpensive part, with the overall repair cost including labor often ranging from around $75 to $200. If the PCB is at fault, parts and labor costs can range from $200 to $600 or more depending on the model and local labor rates. Getting a diagnostic visit from a technician will give you a firm estimate before committing to the repair.

A knowledgeable DIYer can perform basic checks such as reseating thermistor connectors and inspecting the wiring harness for visible damage. Accurate diagnosis also requires a multimeter and a water bath test to compare thermistor resistance against the specified values at a known temperature. However, if the PCB needs replacement, that repair is more involved and may be better suited for a qualified technician familiar with LG systems.

A power reset may temporarily clear the fault display, but error code 1 will return as soon as the PCB re-reads the faulty thermistor or broken circuit. Resetting the unit does not address the underlying hardware problem. The thermistor, its wiring, and the PCB connection all need to be tested and repaired before the code will clear permanently.