Resolve the F3H1 error on a Whirlpool microwave with this troubleshooting guide (2024)

Whirlpool is a popular brand of household microwaves, but like any appliance, they can develop issues over time. One of the common error codes that Whirlpool microwave models can display is F3H1, which usually indicates a problem with the humidity sensor.

If you’re seeing this error message, don’t panic or toss your microwave in the trash just yet! If you’re comfortable with troubleshooting a microwave oven, we have all the steps you need to resolve the F3H1 error code yourself.

If you find out that you need any replacement parts for your Whirlpool 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.

Important: The troubleshooting information 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 F3H1 error code mean?

On Whirlpool microwaves, the F3H1 error specifically points to an issue with the humidity sensor that’s mounted in the oven cavity. This sensor detects the level of humidity released by the food as it heats up.

The microwave’s control board uses input from the humidity sensor to adjust cooking times and power levels automatically. By monitoring the humidity, it can determine how much longer is needed to finish cooking the food inside.

If the control board stops receiving accurate sensor readings, it will likely display the F3H1 error code. The issue usually lies with the sensor itself, the connected wiring, or, in rarer cases, a bad control board.

Read more: How to Clean a Microwave

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.
• 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 insulated 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 and don’t rush while working to prevent accidents and personal injuries.
• Work in a well-lit area so you can clearly see and access the interior parts.
• Clear your workspace of clutter and other obstacles. Keep children and pets away from the work area.
• Never work on internal parts with bare wet hands. Make sure the work area is completely dry.
• Check your user manual to see if there are specific installation or safety instructions for your part or appliance.
• Be gentle when handling or removing parts. Excessive force might damage the appliance or cause injury.
• Wear safety glasses when working with chemicals, dust or cleaning large debris to prevent injury.
• If the appliance has recently been used, give it plenty of time for any heating parts to cool down before working on it.
• Take pictures or make a note of wiring terminals or other connections before disconnecting to prevent any problems with reassembly.
• 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.

Read more: A guide to understanding microwave wattage

How to troubleshoot the F3H1 error code

Find out what’s causing the F3H1 fault code to show up on your Whirlpool microwave by following these steps.

Step 1: Access the humidity sensor

1. Unplug the microwave and open the door.
2. Remove any trim plates protecting the seam between the oven and cabinet.
3. Detach the top cabinet panel above the door by taking out its mounting screws.
4. Carefully remove the top panel to expose the top of the oven cavity.
5. Find the humidity sensor, which resembles a small plastic housing that’s mounted to the cavity ceiling. It’s often near the center or back left side and will have a wire harness routed to the main control board.

Step 2: Inspect the humidity sensor

1. Carefully examine the sensor housing for any cracks or damage. If the housing is damaged, replace it.
2. Inspect the wire harness leading from the sensor. Check for damaged, burned or cut wires, wires pinched under or around other parts and any loose or detached wiring. If the wiring is damaged, replace it.
3. Make sure the wire harness plug is completely inserted into the control board socket.
4. Look for any signs of moisture, grime or grease buildup on the sensor window. Clean it as needed.

If everything looks OK so far, move on to the next step.

Step 3: Test the sensor

1. Make sure the microwave is unplugged.
2. Find the wire harness connector that plugs into the main control board from the humidity sensor.
3. Disconnect the sensor harness plug from the control board.
4. Set a multimeter to resistance mode, usually indicated by the Greek symbol Omega (Ω).
5. Refer to the microwave wiring diagram to find the specific sensor pinout and terminals to test. There may be 2-3 or more pins.
6. Touch the multimeter probes to the correct pins on the sensor connector. Repeat this for each group of pins.
7. Check the resistance reading on the multimeter for each sensor terminal combination.
8. Compare the multimeter readings with the acceptable resistance values in your microwave’s technical sheet or service manual.

If any readings fall outside the specified resistance range for that specific group, then the sensor is defective and needs to be replaced. For example, on some Whirlpool models, the humidity sensor resistance between two pins should be 2520-3080 Ω at room temperature. A reading significantly above or below this range would mean the sensor is faulty.

If the F3H1 issue persists even after replacing the humidity sensor, then the control board may need to be replaced as a last resort.

Read more: 9 safety tips for using a microwave

More information

Thank you for reading! We hope this guide helped you get your Whirlpool 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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