LG Microwave F-7 Error — Sensor Cooking

What Does This Error Mean?

F-7 on an LG microwave means the humidity sensor used by sensor cook features is faulty or contaminated. Manual cooking still works. Clean the sensor grille inside the cavity — persistent F-7 needs sensor replacement.

Affected Models

LG LMC0975ST
LG LMV1831ST
LG LMV2031ST
LG LMHM2237ST
LG LMC1575ST

Common Causes

Grease build-up on the humidity sensor grille
Splashed liquid coating the sensor
Failed humidity sensor component
Sensor wiring loose at the control board

How to Fix It

Confirm manual cooking still works.

Press Time Cook (or equivalent), enter 30 seconds at full power, and run with a cup of water inside. If it heats normally, F-7 is limited to sensor functions and the microwave is still usable manually.
Locate the humidity sensor.

On LG microwaves the humidity sensor is typically a small grille or vent on the upper rear or rear-right wall of the cavity. The exact position varies by model — refer to your manual.
Clean the sensor area.

Wipe the grille with a barely damp cloth. For greasy or sticky residue, use a 50/50 mix of white vinegar and water on the cloth. Do not let liquid drip into the grille — internal moisture causes its own fault.
Power cycle and test.

Unplug for 5 minutes after cleaning, restore power, and try a sensor cook function (such as Reheat). If F-7 has cleared, the issue was sensor contamination.

Frequently Asked Questions

What is the difference between F-3 and F-7 on an LG microwave?

F-3 indicates a touchpad/keypad fault — the buttons themselves are not responding correctly. F-7 indicates a humidity sensor fault — sensor cooking features are disabled but manual buttons still work.

Can grease damage the LG microwave humidity sensor permanently?

Light to moderate grease coating is reversible with cleaning. Heavy build-up over years can corrode the sensor element itself. Routine cleaning every 2–3 months prevents permanent sensor damage.