LG Microwave Error Code F-1

The F-1 code on an LG microwave indicates a fault in the toaster heater circuit or the thermistor that monitors it. The control board has detected either a defective heater element, a defective thermistor, or a loose connection at the CN3 connector on the PCB assembly. The appliance displays this code to alert you that the heating system requires inspection before normal operation can continue.

No, you should not continue using the microwave while F-1 is active. The code indicates the heater circuit is not functioning correctly, and the control board has flagged the fault to prevent unsafe operation. Continuing to run the appliance in this state could cause further damage to the PCB assembly or other components.

Unplugging the microwave and plugging it back in may temporarily clear the F-1 display, but the code will return if the underlying fault is still present. A reset does not repair a defective thermistor, a burned-out heater element, or a loose CN3 connection. The fault must be diagnosed and the root cause corrected to permanently resolve the error.

A knowledgeable DIYer can start by inspecting and reseating the CN3 connector, which requires no replacement parts and sometimes resolves the fault entirely. Testing the thermistor and heater element for continuity requires a multimeter and the ability to safely access internal components. Because microwave interiors contain high-voltage capacitors that can hold a dangerous charge even when unplugged, internal repairs should only be performed by someone familiar with high-voltage safety procedures.

Repair costs depend on the failed component. If only the CN3 connector needs reseating, there may be no parts cost at all, though a service call fee typically ranges from $50 to $100. Replacing a thermistor generally runs $20 to $60 for the part, while a heater element replacement can range from $30 to $80 or more, plus labor. Total repair costs including professional service typically fall between $80 and $200 depending on the component and your location.