How you can troubleshoot an F4 error on a GE microwave

Microwave ovens – convenient as they are – can occasionally malfunction and show error codes like the F4 that may appear on some GE models. But you don’t have to throw out your microwave yet. You’ll be happy to learn that troubleshooting the F4 code is not only easy to do, but doesn’t take much time, either.

If you find out that you need any replacement parts for your GE microwave while you’re troubleshooting, you can 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.

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.

Read more: 9 safety tips for using a microwave

What does the F4 error code mean?

The F4 error code usually indicates that there’s a problem with the humidity sensor in the microwave. Specifically, it means the control board is no longer detecting the humidity sensor signal during an active cooking cycle.

The humidity sensor does what its name suggests: it monitors steam and humidity levels inside the cavity as food cooks. When it’s working correctly, it provides continuous feedback to the control board. Loss of this sensor’s signal mid-cycle can cause the F4 error.

The humidity sensor is a small plastic part that protrudes into the oven cavity. It connects back to the main control board via a wire harness.

Read more: How to Clean a Microwave

Safety tips

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.
• 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 insulated gloves and use insulated tools when testing any parts.
• Check all parts for damage before reassembling and powering up the microwave again.
• Always power off and unplug your appliance or switch off the circuit breaker before you attempt any maintenance or replacement work. This keeps you safe by preventing any risk of electric shock.
• If the appliance has recently been used, give it plenty of time to cool down before working on it.
• 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 see and access appliance parts.
• Keep your workspace free of clutter and other obstacles. Keep children and pets away from the work area.
• Never work on internal parts with wet hands. Make sure the work area is completely dry.
• 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.
• Wear insulated work gloves to protect your hands from sharp metal parts and debris.
• When working with wires, avoid touching any exposed wires or terminals. If you need to touch a wire, use a non-conductive tool or wear insulating gloves to prevent electrical shock.
• Always take photos or make a note of wiring terminals or other connections before disconnecting them to make reassembly easier.
• Don’t test live voltage with a multimeter if you’re unfamiliar with how to prevent short-circuiting.

How to troubleshoot the F4 error

Fix your GE microwave by following these troubleshooting steps.

Step 1: Inspect the humidity sensor

1. Unplug the microwave.
2. Open the door.
3. Find the humidity sensor that’s mounted on the housing inside the cavity.
4. Closely look over the sensor for any visible damage like cracks in the plastic housing or broken connecting pins.
5. Make sure the sensor is securely fastened to the housing. Tighten or reseat it as needed.
6. Make sure the attached wiring has no breaks, frays or burn damage.

Step 2: Check the sensor wiring

• Inspect the wires running from the detached sensor back to the control board socket. Check for any cuts, abrasions, melting, or loose terminals. Replace the wiring harness if needed.
• Make sure the connector is fully inserted into the control board socket. Reseat it if you see any gaps.
• Make sure there isn’t any debris like food or moisture that’s fouling the connector.

Step 3: Perform a sensor quick test

1. Plug the microwave back in (make sure the humidity sensor is installed).
2. Hold buttons 7 and 8 on the keypad at the same time. A number display should appear and indicate the results from the sensor quick test.
3. Check the reading. A normal reading should be between 15 and 185. A reading of less than 6 or higher than 213 means the sensor or the control board is faulty.

If the quick test result is good and there’s no damage to the sensor or wiring, you’ll need to replace the control board as a last resort.

READ MORE: How To Use A Multimeter To Check Appliance Parts

Step 4: Test the microwave (after repairs)

1. Plug the microwave in.
2. Place a small bowl of food or water in the microwave.
3. Run a cooking cycle for 2-3 minutes to make sure the F4 error is cleared.

READ MORE: How to Clean a Microwave

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.

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