F1
LG Microwave
Severity: ModerateWhat Does This Error Mean?
LG microwave F1 means the temperature sensor (thermistor) has detected a fault or an out-of-range temperature reading. Unplug for 60 seconds and test. If F1 returns consistently, the thermistor needs replacement — it is a relatively inexpensive repair.
Affected Models
- LG Over-the-Range Microwave
- LG NeoChef Countertop Microwave
- LG LMV Series
- LG LMVH Series
Common Causes
- Faulty or failed thermistor (temperature sensor) inside the microwave cavity
- Thermistor wiring connector loose
- Microwave genuinely overheated and thermal protection tripped
- Control board fault causing incorrect temperature reading
How to Fix It
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Unplug the microwave for 60 seconds and retry.
If the microwave overheated temporarily (from extended use or a blocked ventilation grille), the thermistor may have triggered a protection fault that clears after cooling. Allow the microwave to cool for 30 minutes after a heavy use session before attempting a reset.
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Check the microwave ventilation.
LG over-the-range microwaves have ventilation grilles on the top and bottom. Ensure the bottom ventilation grille is clear — cookware placed directly under the microwave can trap heat. For countertop models, ensure at least 3 inches of clearance on all sides and the top.
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Have the thermistor tested and replaced.
The thermistor is a small sensor mounted inside the microwave cavity. A technician can test it with a multimeter — a healthy thermistor at room temperature reads approximately 4,000-12,000 ohms. A reading of zero (short) or open circuit (infinite) confirms failure. Thermistors are inexpensive ($10-20) and straightforward to replace.
Frequently Asked Questions
Can I use my LG microwave while the F1 error is showing?
No — LG microwaves lock out operation when an F error code is active. The microwave cannot heat until the fault is cleared. Do not attempt to bypass the error — the thermistor is a safety component.
How much does it cost to fix the F1 error on an LG microwave?
The thermistor part typically costs $15-25. If hiring a technician, total repair cost (parts and labour) is approximately $80-150. For a microwave under 5 years old, repair is usually worthwhile. For older units, weigh the repair cost against replacement.