LG Air Conditioner Error Code 1

Error code 1 on an LG air conditioner means the control board detected a problem with the indoor room temperature thermistor or the indoor pipe temperature thermistor. One or both sensors is reading an open or short circuit, meaning its resistance value is outside the acceptable range. The unit shuts down because it cannot accurately monitor temperatures needed to control cooling.

No. When error code 1 is active, the LG unit will not run normally because the control system has disabled operation due to the thermistor fault. Attempting to bypass or force the unit to run without a functioning temperature sensor risks coil freeze-up, compressor damage from running without proper feedback, or inaccurate cooling that can cause other component failures. Resolve the thermistor fault before operating the unit.

Power down the unit at the breaker before opening the indoor panel. Locate the thermistor assembly, unplug the connectors from the control board, and use a multimeter set to resistance mode. Measure across each thermistor's two leads at a known room temperature. A good thermistor will show a resistance consistent with its NTC temperature curve, commonly around 10k ohms at 77 degrees Fahrenheit, and the reading should decrease smoothly as you warm the sensor with your hand. An open thermistor reads infinite resistance (OL on most meters), and a shorted thermistor reads near zero ohms. Either condition confirms the sensor needs replacement.

Start by inspecting the indoor thermistor assembly and its wiring harness. Power off the unit and check that all thermistor connectors are firmly seated on the control board. Use a multimeter to measure resistance across each thermistor at room temperature and compare the reading to the spec in your service manual, typically around 10k ohms at 77 degrees Fahrenheit for LG units. If a thermistor reads open or near zero, replace it. If resistance values are correct and connectors are secure, the control board input circuit may be at fault.

If the fix is just a loose or corroded connector on the thermistor wiring harness, there is no parts cost. A replacement indoor thermistor for an LG air conditioner typically costs between $10 and $40 for the part depending on the model. If an indoor control board is needed, expect parts costs of $80 to $200 or more. Adding professional labor, a service call to diagnose and replace a thermistor usually runs $100 to $250 total. A homeowner comfortable with basic disassembly and a multimeter can often diagnose and replace the thermistor without professional help.