5 Reasons For KitchenAid Microwave Not Heating (Plus Fixes)

I’ve had the KitchenAid microwave not heating problem twice. And I remember how doubly disappointed I was the second time it happened. But would a unit built by a brand that has become a household name fail to heat in the first place?

Your KitchenAid microwave is not heating because the high-voltage diode failed, the capacitor is faulty, or the magnetron stopped working. It’s also possible that the thermal proctor or the door sensor of your KitchenAid microwave is faulty.

I’ll discuss these five issues in this guide. In particular, I’ll share exactly what you should do to fix the problem to get your KitchenAid microwave heating again. 

Let’s get to it. 

kitchenaid microwave not heating

Why is My KitchenAid Microwave Not Heating? (5 Reasons Explained)

The following table is a summary of why your KitchenAid microwave is not heating as well as what you can do to fix the problem.

 ProblemPossible Solution
1.The high-voltage diode of the microwave may have gone badCheck for visible damages, test the components for continuity and replace if there’s no continuity (if there are no visible damages).
2.The magnetron of your KitchenAid microwave is no longer workingAccess the magnetron and test for continuity (continuity should be zero). Replace the magnetron if there’s no continuity.
3.Your microwave’s door sensor is not workingYou should do a continuity test. Replace the switch with a new one if it doesn’t have continuity.
4.Thermal protector is faultyYou should do a continuity test. Replace the fuses if there’s no continuity (continuity should be zero).
5.The high-voltage capacitor is burnedDischarge the capacitor. Check for visible damages. No visible damages? Test the resistance rating (should be 2 to 3 ohms).

1. The High-Voltage Diode May Be Faulty

Your KitchenAid microwave is not heating or has stopped heating because the high-voltage diode has gone bad.

The purpose of the diode is to convert alternating current (AC) from the capacitor to direct current (DC). Once the conversion is complete, the resulting power is used to power up the magnetron. The magnetron then produce heat required to warm your food.

microwave high voltage diode

If the high-voltage diode malfunctions, the magnetron won’t get sufficient power to operate.  In most cases, the diode burns out, which means it’s easy to assess whether it is bad or otherwise.

If visibly assessing the part is inconclusive, consider using a multimeter to test for continuity. Provided you have had the unit disassembled, testing and replacing the diode shouldn’t take you more than 5 minutes.  

To test the diode for continuity:

  • Cut off the power, unplug the power cord, and unthread and remove the appliance from the kitchen cabinet.
  • Dismantle the unit once you have it on a flat sturdy surface. Make sure you discharge the high-voltage capacitor to avoid electrocution.
  • Find the diode and remove it.
  • Set the multimeter to Rx1 and touch the diode terminals with the multimeter (digital multimeter) probes.

A continuity result of zero (0) means the part is fully functional. Any other result means the diode is bad and needs a replacement.

To replace the faulty diode: 

  • Start by disconnecting the diode end that connects to the high-voltage capacitor and unscrewing the end held by a screw.

Note the connection between the diode and the capacitor so that you can install the new diode appropriately. The magnetron won’t get power if you don’t get the connection right.

  • Install the new diode in the microwave.
  • Reassemble your microwave and it back to the kitchen cabinet.
  • Plug the power cord back into power and restore power.
  • Put a cup of water into the heating chamber to test if the microwave is now heating.

2. The High-Voltage Capacitor May Be Faulty

The KitchenAid microwave high-voltage capacitor works together with the high-voltage diode to convert the power output of the transformer from alternating current (AC) to direct current (DC).

If the high-voltage capacitor burns out, the whole voltage cycle becomes compromised and stops working. As such, the microwave does not heat anything introduced in its heating space.

Use a VOM meter to test the capacitor. Replace the capacitor if faulty.

3. The Magnetron May Have Failed

The magnetron is a part of a KitchenAid microwave that uses a lot of power to generate radiation heat responsible for heating food.

microwave magnetron

The magnetron gets its power from the high-voltage diode. But, as I stated earlier, the high-voltage diode can become faulty. If that happens, the magnetron won’t get enough power to generate the heat required by the microwave to heat food.

If the diode is working fine but the microwave is not heating food, there is a high chance the magnetron is faulty.

First, test the magnetron to determine whether it’s faulty. To do this: 

  • Unplug the microwave from power.
  • Discharge the capacitor to avoid electrocution.
  • Set your multimeter to ohms and rest the magnetron.

The resistance should be between 2 and 3 ohms, which means that you need to replace the magnetron if its resistance does not range between 2 and 3 ohms.

To replace the magnetron:

  • Remove the new magnetron from the packaging.
  • Connect it to the appropriate wires, and secure it with screws.
  • Assemble the microwave.
  • Plug the unit back to power.
  • Put a cup of water in the heating chamber and start the unit to test if the appliance is heating.

4. The Thermal Protector May Have Blown

Your KitchenAid microwave may have stopped heating food because the thermal protector has blown and cut off power.

The thermal protector is the component that trips if the unit overheat. If the thermal protector trips, the microwave will stop heating food and turn off.

Use a multimeter to determine whether the thermal protector has continuity. Replace it if it fails the continuity test. 

5. The Door Sensor is Faulty

A door sensor is one of the most important component of the KitchenAid microwave. Without it, it would be impossible for the microwave to detect whether you’ve actually closed the door.

microwave door sensor

The door sensors must actuate in sequence for the appliance to detect the door is firmly closed.

A KitchenAid microwave may have 3 to 4 door switch sensors depending on the model. If any of the switches fail, the microwave won’t signal the magnetron to start heating.

A microwave door switch can lose continuity and if that happens, you will need to get a new one for replacement.

  • Turn off your power supply and unplug the microwave power code.
  • Unthread the screws holding to the microwave in the kitchen cabinet and the wall bracket, pull the appliance off the cabinet, and place it on a sturdy surface.
  • Unthread the screws holding the grill, pull the grill to remove it, and unthread the screw that holds the control panel and remove it.
  • Unthread the screws securing the door switch assembly and release the door switch assembly by pressing the tab and actuator.
  • With a multimeter, test all the door switches for continuity by touching the terminal with the multimeter probes and pressing the switch on the component to get the readings.

If all the door sensors give a continuity result of zero it means they are functional and the heating problem is somewhere else.

If any or all the switches don’t have a continuity of zero, it means it or they are faulty. In such a case, you’ll need to get a new door switch for replacement.

  • Unpack the new door switch and fix it in the door switch assembly.
  • Realign the door switch assembly to the frame and replace the screws to hold it in place.
  • Connect all the wires disconnected from the control panel appropriately.
  • Fix back the control panel and secure it with screws.
  • Snap the grill into place and rethread its screws to hold.
  • Return the turntable and its support.

With the replacement complete connect the unit pack to power and warm a cup of water to test if the repair took effect.

Related Reading

Frequently Asked Questions

1. Is it Cheaper to Repair a Microwave or Buy a New One?

Repairing or buying a new microwave generally depends on the extent of the damage. A microwave with too many defective parts will cost much to replace.

In addition, the money spent on constant repairs may end up adding to the cost of a new microwave.

My advice is you should first evaluate the extent of the damage to determine whether you need a new microwave or a repair of the one you already have.

2. What is the Most Common Cause of Microwave Failure?

One of the most common problems amongst KitchenAid, Whirlpool, LG, and Samsung microwaves is the failure to heat.

This problem occurs because the magnetron, the component responsible for heating food failed.

More often than not, the magnetron fails to work because the high-voltage diode and high-voltage capacitor are faulty causing the microwave not to heat food.

3. Why Would a Microwave Run But Not Heat?

The door switch might be the reason why your KitchenAid microwave is running but not heating. If the door switch is damaged, the unit doesn’t get a signal that you’ve had the door shut.

If the main control does not receive signals from the door switch, it assumes the unit still has the door opened and doesn’t power the magnetron to start heating food. 

Fortunately, the issue can be resolved by replacing any faulty door switch.

4. What are the Signs that a Microwave is Going Bad?

A KitchenAid microwave can serve you for up to 7 years, but the runtime can be less depending on the frequency of use.

It is after this period that you might start hearing unusual sounds from the unit, food failing to heat properly and the door not closing.

In such instance, it means the unit has served its life, and getting a new microwave is the only best option.

Final Thoughts

I hope that this guide has helped you to know why your KitchenAid microwave is not heating as well as how to fix each potential error.

And the best part is?

None of the solutions that I’ve suggested in this guide requires you to spend money in repair service. That means all you have to do is buy the replacement parts and fix the errors on your own.