LG Microwave Error Code F-3

Reviewed by the ApplianceErrors Editorial Team · Verified against manufacturer service documentation · Last verified: June 10, 2026

⚠ High Severity 👨‍🔧 Call a Pro

Temperature sensor error — over-temperature detected

The most common cause of the F-3 error on a LG microwave is overheating from blocked vents (~50% of cases); start with: check ventilation.

💰 DIY cost: $0–$40 👨‍🔧 Pro cost: $200–$420 Save $200+ by doing it yourself

LG Microwave error code F-3 on the display panel — How the F-3 code appears on a LG microwave display

What Does Error Code F-3 Mean on a LG Microwave?

Temperature sensor error — over-temperature detected.

The control board continuously reads a thermistor mounted in the cavity or near the magnetron. F-3 fires when that sensor reports a temperature above the safe threshold, or when its resistance falls outside the expected range (open or shorted), which the board interprets as an over-temperature or failed-sensor condition. This differs from magnetron or high-voltage faults because the trigger is the thermal reading itself, not power delivery, and it often follows restricted airflow rather than a component burnout.

Models affected: LG countertop and over-the-range microwaves that use a cavity thermistor for temperature monitoring

What owners report: Owners commonly report F-3 appearing after longer cooking sessions or on over-the-range units where grease-clogged vents trap heat. A frequent quick win is simply clearing obstructions and letting the unit cool while unplugged; if the code returns immediately even when cold, the thermistor itself is the more likely culprit.

What Causes Error Code F-3?

Here are the most common causes in order of frequency. Start with the most likely cause before moving to the next:

1

Overheating from blocked vents 50% of cases
2

Temperature sensor failure 35% of cases
3

Control board sensor input failure 15% of cases

How to Fix LG Microwave Error Code F-3

👨‍🔧 Call a Pro Est. time: 1–3 hours

⚡ Safety first: Unplug the appliance before opening any panels or touching internal components.

1

Check ventilation

Ensure the microwave has adequate clearance on all sides. Clean the grille and vent areas.
2

Allow to cool

Unplug for 20 minutes.
3

Test and replace sensor

If error returns after cooling, sensor has likely failed.

🔩 LG microwave thermistor ($15–$40)

⚠️ DANGER: Microwave capacitors hold lethal charge. Only professionals should open microwave cases.

How to Reset Error Code F-3

Unplug 20 minutes and ensure ventilation is clear. If F-3 returns, call a technician.

Note: If the error returns after resetting, the underlying issue has not been resolved. Work through the fix steps above.

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When to Call a Professional

ALWAYS call a professional for internal microwave repairs. Microwave capacitors retain lethal charge even when unplugged.

Average professional repair cost for this issue: $200–$420

Same Code on Other Brands

Error code F-3 appears on these other brands too. See every brand that shows F-3 →

Samsung Microwave F-3

Touchpad/membrane failure

Whirlpool Oven F3

Open oven temperature sensor — sensor circuit open

GE Appliances Oven F3

Oven temperature sensor open circuit

Haier Refrigerator F3

Defrost sensor failure

Find Replacement Parts

Use these links to find the exact replacement parts for your LG Microwave:

🔩

Search PartSelect

LG Microwave repair parts

🔧

Search RepairClinic

Step-by-step video guides

External links — ApplianceErrors.com is not affiliated with these retailers.

More LG Microwave Error Codes

F-6 Keypad/touchpad failure F-11 Shorted key on control panel

Frequently Asked Questions

Can I keep using my LG Microwave when error F-3 appears? +

It is not advisable. The microwave may still power on, but running it while F-3 is active can worsen the sensor fault or damage related parts. Treat it as a soon-as-possible repair.

What most commonly causes F-3 on a LG Microwave? +

Across reported LG microwave repairs, the most frequent is overheating from blocked vents (50% of cases), temperature sensor failure (35%), then control board sensor input failure (15%). Check them in that order before replacing any parts.

F-3 keeps coming back after a reset — what should I check next? +

A reset only clears the stored F-3 fault; if it returns, the sensor problem is still present. Move on to the physical checks — check ventilation, then allow to cool — since the code will reappear until the root cause is resolved. This is a repair most owners hand to a technician.

How much does it cost to fix LG Microwave error F-3? +

A DIY repair typically runs $0–$40 in parts, versus $200–$420 for a professional service call, so handling it yourself saves around $200. Expect the work to take a full service visit.

Which LG Microwave models show error F-3? +

F-3 is documented on LG countertop and over-the-range microwaves that use a cavity thermistor for temperature monitoring. Other units sharing the same control platform can display it too, so the fixes here generally transfer across the series.

Sources & References

• LG Support — Help Library — official manufacturer documentation
• Our editorial & verification policy

Content verified against manufacturer service documentation. Last verified: June 10, 2026.

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