LG Microwave Error Code F-1 — Humidity Sensor Failure
What this means
The F-1 error code on LG microwaves indicates the humidity (steam) sensor is not functioning properly. This sensor detects moisture released by food during cooking and is used by sensor-cook and sensor-reheat programs to automatically determine when food is done. A dirty, damaged, or failed sensor triggers F-1. Manual cooking modes typically continue to work.
Alternate codes: F1
Step-by-step fix
4 stepsClean the humidity sensor
Open the microwave door. The humidity sensor is typically located on the ceiling of the cavity or inside a vent grille. Clean it thoroughly with a soft cloth dampened with warm water and a small amount of mild soap. Remove all food residue and grease film.
Food splatter coating the sensor is the most common cause of F-1. Regular cleaning prevents this error.
Clean the entire interior cavity
Wipe down the interior walls, ceiling, and floor of the microwave cavity. Steam and splatter residue throughout the cavity can affect humidity readings.
Microwave a bowl of water with lemon juice for 3 minutes to loosen stuck-on food, then wipe clean.
Power cycle the microwave
Unplug the microwave for two minutes. Plug it back in and test a sensor-cook function. If the error clears and food cooks properly, the cleaning was sufficient.
If manual mode works but sensor mode still triggers F-1, the sensor itself may need replacement.
Replace the humidity sensor
If cleaning doesn't resolve the error, unplug the microwave and remove the outer cabinet. Locate the humidity sensor, disconnect its wiring, remove the mounting hardware, and install the replacement sensor. Reassemble and test with a sensor-cook cycle.
WARNING: Work only near the sensor area. Do not touch the high-voltage capacitor or magnetron inside the microwave.
When to call a professional
If the sensor has been cleaned and replaced but F-1 persists, the control board's sensor input circuit may be faulty. Due to high-voltage components inside microwaves, professional diagnosis is recommended.
Related error codes
Information compiled from manufacturer service manuals, official troubleshooting documentation, and appliance repair industry resources. This guide is for informational purposes only — always consult a qualified technician for complex repairs.
Learn more about our sourcesParts you may need
Links may earn us a commission at no extra cost to you. We only recommend parts relevant to this repair.