Microwaves are an essential kitchen appliance, allowing you to heat your food conveniently and quickly. But owners of Whirlpool microwaves sometimes have to contend with the problem of their ovens not heating.
Needless to say, this is a troublesome issue to deal with as not only are you not able to heat up your food but diagnosing and fixing the problem can be a challenge if you don’t know what you’re doing.
That’s why in this article, I’m going to explain exactly what causes this microwave issue and give you the very best methods you need to get this problem fixed as easily as possible.
Why is your Whirlpool Microwave Not Heating?
Microwaves heat the food using microwaves which are produced by the magnetron. When a microwave isn’t heating, it is most commonly due to one or more of the components that allow the magnetron to function having failed.
So you’ll need to first diagnose which component is failing and then take steps to get it fixed/replaced.
1. The Timer Function is Turned On
Before we get into specific components, there are a few user settings that may be causing the microwave not to heat.
This is most commonly due to the timer function. When enabled, this will delay the cooking of the food by having a timer that counts down to 0 before it starts.
The purpose of this is for those who need the food to heat by a specific time to fit in with their cooking recipe.
If you’ve forgotten this option by accident, it’s easy to think that the microwave just isn’t working. So here, you’ll need to disable the timer so the food can start to cook straight away.
2. The Door isn’t Fully Closed
The microwave door is an essential part of how the appliance works. As microwaves are harmful to the body, the door uses a mesh grill which is designed to reflect the microwaves back into the appliance, so you are kept nice and safe.
Because it’s part of the microwave safety features, when the door isn’t fully closed, the microwave will not start as it doesn’t want to risk sending harmful microwaves out into your kitchen.
Sometimes the door might not be able to fully close due to a buildup of grease or food, in which case it will need a good clean so it can completely close.
3. The Diode has Failed
To produce microwaves, the magnetron needs a lot of power. So the purpose of the high-voltage diode is to take the incoming AC voltage from your home’s outlet and convert it to DC, which doubles its voltage.
Sometimes the diode can fail or burn out, which means the magnetron won’t get the juice it needs to heat your food. You can often inspect the microwave diode visually for signs of damage, such as blackening or burning.
You can then test it with a multimeter to see if it’s functional or not. If the high-voltage diode is found to be non-functional, then it will need to be replaced with a new one.
4. The Door Switch is Defective
I previously mentioned that the door needs to be fully closed, or the microwave won’t turn on. In some cases, the door switch can fail, which causes the microwave to believe it’s still open, even though it has physically latched.
The door switch mechanism is designed to create a full circuit between two contacts which lets the microwave know the doors are closed.
You will need to test the switch for continuity, and if it’s found to be broken, it should be replaced.
5. The Magnetron has Burned Out
The microwave magnetron is the component that physically produces the microwaves that heat your food.
As magnetrons age, they tend to wear down and burn out to the point where they are no longer producing enough microwaves to heat your food properly.
As these are quite complicated devices and are challenging to self-repair. They will usually be replaced with new ones.
6. The High-Voltage Capacitor has Failed
The high-voltage capacitor works together with the diode to double the voltage supplied from your power outlet, which then powers the magnetron.
So when the capacitor fails, even if the voltage diode is working just fine, your microwave still won’t be able to produce enough juice to power the microwave. So once again, it will need to be replaced.
7. The Thermal Fuse has Blown
The thermal fuse is a safety component that monitors the internal temperature of the microwave. When this temperature reaches a dangerous level that presents a risk of fire or potential damage to the microwave, the fuse will blow itself and immediately cut power to the microwave.
Thermal fuses are single-use components, so once blown, your only option is to replace them.
8. A Main Control Board Issue
The main control board acts as the brain of the microwave, sending out instructions to the various components based on user inputs from the front control panel.
So when the control board starts to have problems, one or more of the internal components may not work properly, resulting in your microwave not heating.
However, as control boards are quite complicated components, they are difficult to repair, so the usual course of action is just to replace the control board with a new one.
How to Fix a Whirlpool Microwave Not Heating?
As you can see, if any of the components associated with the production of the microwaves that heat the food fail or burn out, there’s a good chance your microwave can’t get enough power and produce the heat required to cook the food.
So you’ll need to go through and replace the faulty components before your microwave can work properly.
1. Ensure the Timer Function is Disabled
If the timer function is enabled, there will be a countdown before the microwave starts to heat. So you need to turn this option off to ensure your whirlpool microwave oven will begin working as soon as you press start.
To do this, all you need to do is locate the ‘timer’ button, which is usually placed on the number pad in the bottom right. On some models, it may be located on the top right with the ‘Timer Set/Off’ text.
If the timer is already counting down, you can press this button to bypass the timer function. Alternatively, you can also press the cancel button.
2. Ensure the Door can Fully Close
When a microwave door can’t fully close, the door switch can’t engage, preventing the whirlpool microwave oven from starting.
So you should inspect the door for anything that is preventing the door from making a full connection to the frame.
This is most commonly due to a piece of food or a buildup of crumbs/grease. You should clean the door frame and latches thoroughly with hot soapy water to remove this buildup.
3. Replace the Faulty Voltage Diode
If a microwave diode fails, the incoming power won’t be amplified enough to power the magnetron. So once the diode has been tested and found to be faulty, it will need to be replaced.
- Start by unplugging the microwave from the power supply.
- Take out the microwave turntable and unscrew the panel which covers the diode.
- For safety reasons, you will need to discharge the capacitors before proceeding.
- Remove the diode screw and disconnect it from the microwave capacitor. It’s a good idea to take a picture using your phone, so you can refer to it when installing the new one.
- Install the new diode, ensuring it has the right polarity and the wires are plugged in the exact same way as the old one was.
- Now you can re-assemble the microwave and plug it back in.
4. The Door Switch is Defective
If a door switch is defective, the microwave won’t turn on even when the door is physically latched in place. So they will need to be replaced.
- Start by unplugging the microwave from the power supply.
- Remove the grill, control panel, and switch assembly to gain access to the door switch.
- You will find a release tab that allows you to pop out the door switch wires; gently press this in to release the broken door switch and unplug any attached wires.
- Install the new door switch in its place and attach the wires using the same configuration that the old switch used.
- Push the new door switch back into place, and re-install the switch assembly, control panel, and grill.
5. Replace the Magnetron
Once the magnetron has burned out, the only option is to replace it. However, as this is quite an involved process, we recommend contacting Whirlpool customer support, who will arrange for a replacement magnetron and for an experienced appliance technician to come out and help you install it.
6. Install a New High-Voltage Capacitor
Because high-voltage capacitors use the very high current demanded by microwave ovens, repairing or installing a new microwave capacitor can pose a serious health risk.
So if you are not already correctly trained in how to perform this, you must contact Whirlpool support and get a qualified appliance technician to do this for you.
7. Replace the Thermal Fuse
Once a thermal fuse has blown, the only option is to replace it, as these as single-use components.
- As always, begin by unplugging the microwave from the power source.
- Remove the screws which attach the outer casing and pull the shell away from the microwave to reveal the thermal fuse.
- Once the thermal fuse has been located (you can refer to your user manual to find the correct location for your specific microwave model), you can unplug the wires and remove the screw attaching it to the microwave.
- Pull the old fuse out, discard it, and install the new one in its place.
- Plug the two wires back in using the same configuration as the old fuse and screw it back into place.
- You can re-install the outer shell and plug it into the power supply.
8. Replace the Control Board
Usually, when there is a defective control board, it will just need to be replaced, as the process of diagnosing and fixing it is more trouble than it’s worth.
Here you should reach out to a trained technician or Whirlpool support to have the bad control board removed and the new one installed in its place.
Adrian is an ISCET licensed professional that has completed the National Appliance Service Technician Certification Exam and has the expertise to diagnose and repair any appliance. He is well-versed in the latest technologies and techniques and is always up-to-date on the latest industry standards.
