Why Is My Microwave Not Heating?

Jul 29, 2023, 12:55pm

If the microwave does not heat up despite the fact that it is well supplied with electricity, then it will be necessary to test the various components and understand the symptoms. When faced with a microwave failure, the first thing to do is to diagnose the failure by checking the different parts:

  • noise filter
  • the magnetron
  • the transformer
  • the electronic card
  • the capacitor

The microwave will not heat if any of these parts fail.

Microwaves have become an essential kitchen appliance for their convenience and speed. However, when a microwave stops heating food, it can be a frustrating experience. If your microwave is running but not heating your food, there could be a variety of reasons for this. Let’s explore these issues and what you can do about them.

Why Is My Microwave Not Heating?

Problem with the High Voltage Diode

The high voltage diode is a component that helps provide the power needed to generate the microwaves that heat your food. If the diode burns out, the microwave won’t heat even though it runs.


The diode can be tested and replaced if needed, but this repair involves high voltages which can be dangerous. Therefore, it’s advised to have a professional technician handle this repair.

Faulty Door Switch

Microwaves have door switches that send a signal to start heating when the door is securely closed. If one of the door switches is faulty, the microwave might not detect that the door is closed and therefore won’t activate the heating function.


A technician can test the door switches with a multimeter and replace a faulty switch if necessary.

Broken Magnetron

The magnetron is the component in the microwave that generates the microwaves. A faulty magnetron is one of the most common causes of a microwave not heating.


Replacing a magnetron is a complex and potentially dangerous task due to the high voltage involved. It’s best left to professionals. Keep in mind that if your microwave is older, replacing the entire unit might be more cost-effective than replacing the magnetron.

Why Is My Microwave Not Heating?

Malfunctioning Thermal Fuse

The thermal fuse is a safety device that shuts off the microwave if it overheats. If the thermal fuse has blown, the microwave may turn on, but it won’t heat.


A blown thermal fuse needs to be replaced. Because of the high electrical charge even when the microwave is unplugged, it’s recommended to have a professional replace the fuse.

Damaged Capacitor

The capacitor stores electricity and works with the diode and magnetron to heat the food. If the capacitor is damaged, the microwave may not heat.


A damaged capacitor should be replaced by a professional, as it can store a dangerous electrical charge even when the microwave is unplugged.

In conclusion, a microwave that’s not heating is likely due to a problem with one of its internal components. Some issues might be resolved by resetting the microwave, but often, component failure will require professional repair or replacement. Always consult with a professional if you’re unsure of how to fix the problem, to avoid risk of injury or further damage to the microwave. Regular maintenance can also help prevent these issues and prolong the lifespan of your appliance.