5 Reasons Your Whirlpool Microwave Is Not Heating

This troubleshooting guide aims to help you diagnose why your Whirlpool microwave is not heating, and guide you through practical actions towards a successful outcome.

I will walk you through a number of simple checks, and step-by-step solutions, ensuring that you can safely get your appliance back to optimal operation, without unnecessary costs or hassle. Always remember, if in doubt, it’s best to consult with a professional appliance technician.

Whirlpool Microwave Is Not Heating?

There are several reasons why your Whirlpool microwave isn’t producing enough heat to warm your food, including: faulty door switches, a faulty magnetron, a broken diode, or a possibly an issue with the high-voltage capacitor. Other possible causes include a poor thermal cut-out or issues with the microwave’s control board.

Let’s work through each possible cause, clarify exactly what’s happening and recommend steps to troubleshoot the problem.

1.      Burned Out Diode 

The diode is a small electrical component that works in conjunction with the microwave’s capacitor to double the voltage supplied to the magnetron. The magnetron is the element that produces the heat, which we will talk about in more detail later. When the diode burns out, the magnetron cannot receive the voltage it needs which prevents it producing the required level of heat.

Like all electrical and mechanical components the diode can burn out over time with wear and tear. It can also be caused by a local power surge. If you hear a loud humming noise when your microwave is switched on that is a strong indicator that the diode is at fault.

Testing The Diode

1. Disconnect the microwave from the power source to prevent a shock.
2. Remove the microwave casing and locate the diode, which is typically connected to the capacitor.
3. Conduct a visual inspection of the diode, if it looks burned out or damaged in any way, it will need replacing
4. You can also test the diode for continuity using a multimeter. Set the multimeter to the highest resistance scale, touch the probes to the diode’s terminals. You should see high resistance in one direction and low in the other, indicating that the diode is functioning okay.
5. If it reads high or zero in both directions, it’s faulty and needs replacing.

To replace a burned-out diode, you’ll need to purchase a new diode compatible with your microwave model. After disconnecting the microwave from the power source, remove the old diode from the capacitor and the chassis, and replace it with the new one.

Caution: Microwaves can contain lethal voltages. Only proceed if confident in your abilities; otherwise, hire a professional.

How to test a microwave oven diode high voltage CL01-12 / como probar un diodo de microondas HV

2.  Faulty Door Switches 

The door switch on your microwave is a safety feature that ensures the appliance only operates when the door is securely closed. This prevents any potential exposure to harmful microwaves. If door switch fails, the microwave control board can receive a signal that the door is open, preventing it from heating as a precaution.

The door switch will fail as a result of normal wear and tear, or if the door is overused or slammed shut. If the microwave light or fan is working but your food is not heating, it’s a strong indication that the door switch is defective.

Testing The Door Switch

1. As with all maintenance work, first disconnect the microwave by unplugging it.
2. Look around the perimeter of the door and locate the door switches. There are usually three, switches in the door latch assembly.
3. Use your multimeter to test each switch for continuity, which should change as the switch button is activated or released.
4. If a switch doesn’t change, it’s most likely faulty and needs replacing.

To replace a faulty switch, note its position and connections before removing it. I usually recommend taking a photograph to help you reposition and reassembly the component you are replacing. Install the new switch by reconnecting the wires as they were before.

Caution: Working with electrical appliances can be dangerous if you’re not familiar with safe practices. If you’re unsure, consider hiring a professional.

3.     Worn Magnetron 

The magnetron is the part of the microwave that generate the ‘microwaves’ that heats your food. If the magnetron is burnt out or defective, the microwave won’t be able to produce heat. A damaged magnetron cannot be fixed, so it will have to be replaced, but first we need to test it to diagnose if the magnetron is the problem.

Testing a magnetron involves working with a high-voltage device, so I recommended leaving this task to a professional. However, if you’re confident in your abilities, here’s how you can do it:

1. First unplug the microwave unplug the microwave from the main power source.
2. Remove the microwave outer cover, which is usually secured by screws along the back or side. Beware even when unplugged, the microwave capacitor can hold a high-voltage charge.
3. Release the capacity charge with an insulated screwdriver by creating a short circuit between the capacitor terminals. You will hear a click as you discharge any residual electricity. Always proceed with caution.
4. Next locate the magnetron, which is the largest component and is usually located near the center of the microwave. See the image above to help you identify the magnetron.
5. Remove the magnetron, by carefully disconnecting the wires and removing the retaining screws.
6. You can test the magnetron with a multimeter. Set it to the resistance scale and test it  between the terminals. It should read less than one ohm.
7. Next, test between each terminal and the magnetron casing. This should read infinity, which will indicate no continuity.
8. If either of these tests fail, it is likely that the magnetron is faulty and needs replacing.

If the magnetron needs replacing, you will need to purchase a new component that is compatible with your microwave model. A replacement Magnetron will cost around $180. So at this point, you may want to decide if it warrants the cost or if you simply buy a new machine.

How to test a good and bad microwave oven Magnetron

4.     Faulty High-Voltage Capacitor 

Microwaves are complex machines, with a lot of different electrical components in play. The capacitor, for example, is one part that works in conjunction with the diode to power up the appliance, allowing it to heat.

If the capacitor is broken, you may get a mild burning smell, as the electrical circuit that powers your microwave won’t be complete, preventing the appliance from functioning. 

To test the capacitor from your microwave, you’ll need to plug it into a power outlet and use a VOM or Volt-Ohm Meter to measure it. You should see a VOM reading of 10 microfarads or more. If the reading is lower, the capacitor is likely broken and will need replacing.

How to test microwave HV capacitor using multimeter/ good vs bad

5.     Faulty High-Voltage Transformer

The microwave’s high-voltage transformer ramps up standard household electrical voltage to the level required for the magnetron to produce microwaves. It basically receives a low-voltage AC from the household power supply and transforms it into high-voltage AC, then sends it to power the magnetron.

If the transformer fails or breaks down, you may start to see sparks or even smoke inside the appliance. Clearly, this is a safety hazard and needs the switching off immediately.

The microwave’s high-voltage transformer ramps up standard household electrical voltage to the level required for the magnetron to produce microwaves. It basically receives a low-voltage AC from the household power supply and transforms it into high-voltage AC, then sends it to power the magnetron.

1. To test the high-Voltage Transformer, unplug the microwave and discharge the capacitor an insulated screwdriver by creating a short circuit between the capacitor terminals. You should hear a clicking noise as the residual electricity is discharged  
2. Using a multimeter set to the resistance scale, test between the transformer’s primary and secondary windings. If there’s no continuity, the multimeter will show infinity, confirming that the transformer is defective.

Be sure to follow all standard safety precautions when working with high-voltage components.

You can test your microwave transformer by following the step-by-step instructions in the video below.

Microwave Not Heating And Noisy When Running 

Some users notice a buzzing noise that appears when their microwave stops heating. This can be a worrying sign, and it clearly shows that something isn’t right with your device. 

Worn Diode or Magnetron 

Usually, if you hear a noise when your microwave is running, and it fails to heat correctly, it’s the diode at fault and it will need to be replaced.

The other possible explanation is a faulty magnetron, which I explained earlier will prevent the microwave from heating food, and will also cause a distinct hum or buzzing sound.

Microwave Not Turning and Not Heating  

If your microwave isn’t turning, the turntable motor is likely to blame. This is the component that powers up the rotating turntable that you put bowls and plates and other items on when you place them in the microwave.

The easiest way to spot this issue is to simply open the microwave, check that the turntable is in position, and then close it and turn it on. If the table doesn’t move, this suggests that there is something wrong with the motor. You can remove the motor and simply spin the axle to see if it turns freely.

Fixing a Whirlpool Microwave That Is Not Heating 

So, what can you do if your Whirlpool microwave isn’t heating? Well, in most cases, it is possible to repair the microwave, which usually involves one or two replacement components. But before you book any repairs, you need to think about two things: warranty and value.

Is It Still Under Warranty?

First, check to see if your microwave is still under warranty. If it is, then it’s possible that you can get a repair or replacement as part of your cover.

Is It Worth Fixing Or Buying A New Microwave?

If you don’t have a warranty, you’ll have to cover the costs of the repairs yourself. This is where you need to think about the value for money of repairs versus a potential replacement microwave. Simple repairs such as a new door switch won’t cost much at all, but other repairs can be more costly. So if your microwave is quite old and has had multiple issues, it may be better value to simply get a new one, rather than having to pay the costs of repairs over and over.

Whirlpool Microwave Not Heating: Solved

As you can see, there are plenty of potential problems that may arise with a Whirlpool microwave, but if you can figure out the cause of the problem, you may be able to repair your microwave and start using it once again. Hopefully, this guide has helped you find out why your Whirlpool microwave might not work properly.

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