F1 error on a GE microwave: A troubleshooting guide

Don’t let the F1 error on your GE microwave slow down your food preparation. This code might show up if there’s an issue with the thermal sensor (also known as a thermistor) in the microwave, but thankfully you can resolve it yourself.

If you find out that you need any replacement parts for your GE microwave, just enter your model number at AppliancePartsPros.com to order them. Most orders arrive in just two business days, and we have thousands of free guides to show you how to install your new parts.

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Disclaimer: The error code information provided in this article is based on general service manuals and may not apply to your specific appliance model. While we strive to offer helpful advice for DIY appliance repairs, variations in models and configurations can lead to differences in troubleshooting steps, error codes and part replacements. For the most accurate guidance, we strongly recommend consulting the technical sheet for your specific appliance model.

What does the F1 error code mean?

The F1 display usually indicates that the thermal sensor is open due to excessively high temperatures in the microwave cavity.

This can also happen if a large food item from the fridge is placed in the microwave and must cook for more than 5 minutes. If this is the case, the thermistor resistance won’t change fast enough, resulting in the F1 error. The error can often be cleared at the end of the cycle so the microwave can continue cooking.

The thermal sensor monitors the internal air temperature in the cavity where food is cooked. It provides a closed-loop feedback reading to the microwave’s control board. If the sensor circuit opens, the microwave will shut down and display the F1 error to prevent dangerously high temperatures.

Safety precautions

Microwaves contain high-voltage parts and can store voltage even when they’re disconnected from a power source. Please be very careful while working on a microwave’s internal parts to avoid electrocution, which has the potential to cause serious injuries or death.

• Always unplug the microwave before troubleshooting or making repairs.
• If the microwave has recently been used, give it plenty of time to cool down before working on it.
• Discharge the high-voltage capacitor before working on high-voltage parts to eliminate the risk of electric shock.
• Never attempt to run the microwave while its casing is open or when internal parts are exposed. Always completely reassemble the microwave before testing or using it.
• Never attempt to bypass any microwave safety features.
• With the microwave unplugged, remove the outer case to gain internal access.
• Wear insulating gloves and use insulated tools when testing any parts.
• Check all parts for damage before reassembling and powering up the microwave again.
• Take your time while working to prevent accidents and personal injuries. Rushing is the enemy of precision.
• Work in a well-lit area so you can clearly see and access appliance parts.
• Keep your workspace free of clutter and other obstacles. Keep children and pets away from the work area.
• Check the user manual to see if there are specific installation or safety instructions related to your appliance or replacement part.
• Be gentle when handling or removing parts. Excessive force might damage the appliance or cause personal injury.
• Don’t test live voltage with a multimeter if you’re unfamiliar with how to prevent short-circuiting.
• Consider wearing safety glasses and/or a dust mask when working with chemicals, dust or a large amount of debris to prevent irritation or injury.

Read more: How to Clean a Microwave

Troubleshooting instructions

The thermal sensor can be found on the microwave oven’s cavity wall, protruding into the interior space. It’s usually mounted into a plastic housing that’s attached to the right cavity wall. There will also be wiring connecting the sensor back to the oven’s main control board where it goes into a socket or connector.

Step 1 – Check the ventilation

Obstructions in the microwave’s airflow and ventilation can cause it to overheat and display an F1 error.

Check and clear any ventilation openings, fans and filters so the heat can dissipate.

Step 2 – Inspect the thermal sensor

1. Unplug the microwave.
2. Remove the outer case panels to access the internal cavity.
3. Find the thermal sensor and examine it closely. Look for any signs of physical damage like cracks or burning.
4. Make sure the sensor is firmly seated in the cavity wall housing.

Step 3 – Check the wires

1. With the thermal sensor unplugged, visually trace the connecting wires back to the control board. Inspect the wiring for damage, charring, or melting.
2. Check for any areas where insulation has cracked or where the wires have poor connections.

Reconnect any loose wire terminals that you find. Replace or repair any severely damaged wiring that could be disrupting the sensor readings.

Step 4 – Test the sensor

1. Make sure the microwave is still unplugged.
2. Set a multimeter to the resistance setting (Ω).
3. Detach the sensor wiring and place the meter probes across its terminals.
4. Check the meter reading. The sensor should read around 224,000 to 310,000 ohms at room temperature (70°F). If resistance is significantly higher, it likely indicates an open circuit failure in the sensor from damage due to overheating.

Replace the sensor if its resistance is far out of the normal range.

Read more: How To Clean A Microwave Grease Filter

Step 5 – Check the control board

If the thermal sensor itself is functioning correctly, then the F1 error is likely caused by a faulty control board.

You can use a multimeter to test the board to make sure it’s receiving 120 volts AC at the proper terminals. These terminals vary from board to board, so make sure to check your microwave’s wiring diagram so you can test the correct ones.

Step 6 – Final checks

After replacing any damaged parts, fully reassemble the microwave.

Plug it back in and run it through a complete cook cycle with a small bowl of water or food to see if the F1 error code is gone.

Read more: 10 reasons why a microwave won’t heat

More information

Thank you for reading! We hope this guide helped you get your GE microwave working again.

If you have any other appliance repair needs or projects, don’t hesitate to explore our other troubleshooting guides and videos.

If you need replacement parts or some extra help with ordering them, grab your model number and head over to AppliancePartsPros.com, where you can chat with a pro, read our DIY blog and more. We can also help you troubleshoot common microwave problems here.

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