What this code means
The F16 code on an LG microwave signals a heating-related fault. LG’s official support documentation identifies F16 as a heating issue detected, and technician-level fault-code charts narrow this to an inverter heat sink error. The inverter is the power module that converts AC current to the high voltage needed for the magnetron to heat food. When the inverter or its heat sink overheats or fails, the control board throws F16 and stops the microwave to prevent damage.
This code points to the microwave’s power and heating circuit rather than user-resettable issues like door latches or keypads. Because it involves the high-voltage inverter assembly, F16 typically requires service rather than a DIY fix.
Before You Replace Anything
Many owners assume F16 is a control-board or keypad fault and replace the main board first. Always verify that the cooling fan runs and vents are clear before ordering any parts, since a stuck fan will overheat a healthy inverter.
Common Causes
- Failed inverter module The inverter assembly itself has failed due to age, power surges, or internal component breakdown, triggering the heat sink error.
- Cooling fan motor failure If the cooling fan stops running or runs too slowly, the inverter heat sink cannot dissipate heat and the control flags F16.
- Blocked vents or airflow obstruction Dust, grease, or external blockage prevents air from reaching the inverter heat sink, causing it to overheat even when the fan runs.
- Loose or corroded inverter wiring Connector faults or broken harness wires in the inverter circuit create high resistance and heat, tripping the sensor.
Step-by-Step Fix
- Unplug the microwave or switch off the circuit breaker and wait 60 seconds to reset the control board and clear any transient fault.
- Plug back in and test by running a one-minute heating cycle with a cup of water to see whether F16 returns immediately or during heating.
- Inspect and clean all vents on the sides, top, and rear of the microwave cabinet to confirm airflow is not obstructed by dust or grease.
- Listen for the cooling fan when you start the microwave. If the fan does not spin or sounds weak, the fan motor may be failing and causing inverter overheating.
- Disconnect power again and remove the outer cabinet panels following your model’s service manual to access the inverter module and fan assembly.
- Check inverter wiring and connectors for signs of heat damage, loose plugs, burnt insulation, or corrosion at all harness points in the inverter circuit.
- Replace the inverter module and/or cooling fan motor as diagnosed, reconnect all harnesses, reassemble the cabinet, and retest under load to confirm the code does not recur.
Parts Often Needed
| Part | Notes |
|---|---|
| LG microwave inverter module (assembly) | Amazon | Verify your exact model number before ordering; inverter part numbers vary by microwave series and power rating. |
| LG microwave cooling fan motor | Amazon | Order the OEM motor for your model if the fan does not run or runs slowly during operation. |
When to Call a Pro
Call a professional appliance technician as soon as F16 appears and persists after a power reset. The inverter section operates at high voltage and requires proper discharge, test equipment, and safety procedures that go beyond typical homeowner tools. Technicians will verify whether the inverter module, cooling fan, or associated wiring has failed, replace the faulty component, and retest the microwave under load to confirm safe operation. Attempting inverter work without training risks electric shock and further damage to expensive control boards.