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Error code reference

Whirlpool Microwave Error Code -F3-

Thermistor failure

Whirlpool codesWhirlpool microwave codes

Thermistor failure — error will occur if the oven cavity temperature fails to change during convection operation.

First step from the service manual

Verify that the heating element is working correctly before replacing the thermistor.

The complete diagnostic procedure includes additional test steps, resistance specifications, wiring diagram references, and component test points.

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  • Step-by-step tests with expected resistance, voltage, and continuity values
  • Wiring diagram references and connector pinouts from the OEM service manual
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What -F3- means on a Whirlpool microwave

The -F3- error code on a Whirlpool microwave indicates a thermistor failure detected during convection operation. The thermistor is a temperature-sensing resistor located in the oven cavity that monitors internal temperature and reports readings to the control board. During convection cooking, the control board expects to see a measurable rise in cavity temperature as the heating element operates. If the temperature reading fails to change within the expected timeframe, the board interprets this as a thermistor fault and displays the -F3- code.

The critical distinction with this error is that the problem may not originate with the thermistor itself. The heating element must be verified as functional before assuming the sensor has failed. If the element is not producing heat, the cavity temperature will genuinely remain static, which produces the same symptom as a failed thermistor. This is why the recommended first diagnostic step is to confirm the heating element is operating correctly.

If the heating element is confirmed to be working, attention shifts to the thermistor and its wiring. A thermistor that has drifted out of its expected resistance range, developed an open circuit, or has a damaged connector will report a flat or implausible temperature reading to the control board. Wiring harness damage between the thermistor and the control board can produce the same result. Resistance values for the thermistor should be checked against the specification for the specific model to determine if the sensor is within tolerance.

Source: manufacturer service documentation.

Common causes of -F3-

  1. 01

    Faulty heating element

    Part replacement

    If the convection heating element is not producing heat, the cavity temperature will not rise and the control board will trigger the -F3- error. Inspect the element for visible breaks or burns, and test for continuity before replacing the thermistor.

  2. 02

    Failed thermistor

    Part replacement

    The thermistor may have an open circuit, a short, or resistance values outside the acceptable range for the model. Testing the thermistor with a multimeter and comparing readings to the model specification will confirm whether it needs replacement.

  3. 03

    Damaged thermistor wiring or connector

    Wiring / connection

    The wiring harness connecting the thermistor to the control board can develop breaks, burns, or loose connectors, causing the board to receive no signal or an incorrect one. Visually inspect the harness and connector pins for damage or corrosion.

  4. 04

    Control board failure

    Part replacement

    If the thermistor and heating element both test correctly and the wiring is intact, the control board itself may be misreading or failing to process the thermistor signal. This is a less common cause and should be diagnosed after ruling out the other components.

See the test procedure for each cause

Frequently asked questions about -F3-

What does -F3- mean on a Whirlpool microwave?
The -F3- error code indicates a thermistor failure detected during convection operation. Specifically, the control board monitored the oven cavity temperature and found that it did not change as expected while the convection system was running. This points to a problem with the thermistor, the heating element, or the wiring between the sensor and the control board.
Can I fix the -F3- error myself, or do I need a technician?
A knowledgeable DIYer can perform basic diagnostics such as visually inspecting the heating element and wiring harness, and testing the thermistor with a multimeter. However, working inside a microwave involves high-voltage components including a capacitor that can retain a dangerous charge even when unplugged. If you are not comfortable safely discharging the capacitor and working around high-voltage parts, a qualified technician should perform the repair.
Is it safe to use my Whirlpool microwave while the -F3- error is showing?
No. The -F3- error indicates the convection system is not operating correctly and the oven has likely stopped heating as a safety measure. Continuing to use the appliance in this state could produce uneven or no cooking results and may risk further component damage. The microwave should not be used until the fault is diagnosed and repaired.
How much does it cost to repair a -F3- error on a Whirlpool microwave?
Repair costs vary depending on which component has failed. A replacement thermistor typically falls in the range of $15 to $50 for the part alone, while a heating element can range from $30 to $80 or more depending on the model. If professional labor is needed, total repair costs including parts and service can range from $100 to $250 or higher.
Will resetting my Whirlpool microwave clear the -F3- error code?
Resetting the microwave by unplugging it for a few minutes may temporarily clear the error display, but the code will return as soon as the microwave attempts to run a convection cycle again if the underlying problem has not been fixed. A reset does not repair the thermistor, heating element, or wiring. The root cause must be diagnosed and corrected for the error to be permanently resolved.

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