LG Dishwasher Error Code F-3

The F-3 code means the control board has detected a temperature above 180°F, or it has found a short circuit in the thermistor circuit. The thermistor is the sensor that monitors water and air temperature inside the dishwasher. Because of this fault, the dryer function is disabled. The root cause can be a wiring short, a failed thermistor, or an actual overheating condition from a blocked vent.

Start by checking the vent for any obstruction and clearing it if blocked. Next, inspect the thermistor wiring harness for damaged insulation or a pinched wire causing a short circuit. If the wiring looks intact, use a multimeter to test the thermistor's resistance; a reading that is out of the manufacturer's specified range indicates the thermistor needs to be replaced. If both the wiring and thermistor test correctly, the control board may be at fault and should be evaluated by a technician.

Yes. A short circuit in the thermistor wiring or within the thermistor itself will cause the control board to receive a signal it interprets as an extremely high temperature, triggering F-3 even when the actual tub temperature is completely normal. This is why checking for a short circuit in the thermistor circuit is the first recommended step, since it is a common cause of F-3 codes that appear without any real overheating event.

Running the dishwasher with an active F-3 code is not recommended. If the code reflects a real overheating condition caused by restricted venting, continued use could cause damage to internal components or the surrounding cabinetry. If it is a false reading from a shorted thermistor or wiring fault, the drying cycle will not function correctly and the appliance is not operating as designed. Diagnose and resolve the cause before resuming normal use.

If the fix is simply clearing a blocked vent, the cost is nothing beyond your time. A replacement thermistor is typically an inexpensive part, often in the $15 to $40 range, and is a manageable DIY repair for someone comfortable using a multimeter and accessing the interior of the dishwasher. If the control board is the cause, parts and labor from a technician can bring the total to $150 to $300 or more depending on your region and the specific model.