LG Microwave Error Code F-5 — Humidity Sensor Open Circuit
What this means
The F-5 error code on LG microwaves indicates the humidity (steam) sensor has an open circuit — there is no electrical path through the sensor or its wiring. Unlike F-1 which can be a general sensor malfunction, F-5 specifically points to a broken connection. The sensor wire may be severed, the connector may be loose, or the sensor element itself has failed open. Sensor-cook modes will not work, though manual cooking may still function.
Alternate codes: F5
Step-by-step fix
4 stepsPower cycle the microwave
Unplug the microwave for two minutes and plug it back in. Test a sensor-cook function. A loose wire that made temporary contact during a vibration can cause a transient F-5.
If the error appears only intermittently, the connection is probably loose rather than fully broken.
Check the humidity sensor connector
Unplug the microwave. Remove the outer cabinet. Locate the humidity sensor wiring harness connection to the control board. Unplug it, inspect for corrosion or bent pins, and firmly reseat it.
WARNING: Do not touch the high-voltage capacitor. Work only near the sensor and control board.
Test the sensor for continuity
With the sensor disconnected, measure its resistance with a multimeter. The expected range varies by model (check the tech sheet), but an OL (open line) reading confirms the sensor or wiring is broken.
Test at both the sensor end and the board connector end to isolate whether the break is in the sensor itself or the wiring.
Replace the humidity sensor
If the sensor reads OL, replace it. Remove the mounting hardware, disconnect the old sensor, and install the new one. Reassemble and test with a sensor-cook cycle.
Route the new sensor's wires carefully to avoid pinch points that could cause future open circuits.
When to call a professional
If the sensor and wiring both test good but F-5 persists, the control board's sensor input may be faulty. Due to high-voltage components, a technician should handle further diagnosis.
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.
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