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Microwave will not heat up
Common reasons your microwave will not heat up
The most common reasons your microwave won't heat up are a bad thermostat, malfunctioning electronic control board or a broken switch.
48% of the time it's the Thermostat
23% of the time it's the Electronic Control Board
15% of the time it's the Switch
14% of the time it's the Something else
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Common microwave repair parts you may need
Replacing one of these microwave parts may fix your problem.
Thermostat Replacement
A faulty thermostat in a microwave can lead to various issues, primarily affecting the power supply to its components. Microwaves are equipped with multiple internal thermostats designed to safeguard against hazards if components fail. For instance, many microwaves feature a magnetron thermostat, which triggers in response to excessive current or temperature in the magnetron area. Another thermostat oversees the cooking cavity temperature and activates when it exceeds safe levels. If any of these thermostats trip, the microwave will fail to start, and its lights, fans, and display will cease to function. Due to the presence of high-voltage components like transformers and capacitors, which can retain dangerous levels of electricity even after unplugging, it's advisable to have a Sears Home Services professional inspect and repair the microwave.
Electronic Control Board Replacement
When a microwave's electronic control board malfunctions, it can trigger various issues, such as power loss, lack of heating, or difficulty turning off. This happens because the control board acts as the microwave's central command system, overseeing critical functions like heating elements, cooling fans, lighting, turntable movement, cooking duration, power levels, and display functions. A malfunctioning control board can disrupt communication among these components. Signs of a failing board include unusual noises like chattering or clicking, or the emission of a burning odor. Considering the potential repercussions on multiple components, it's prudent to have a Sears Home Services professional conduct diagnostic tests on the board to determine if replacement is necessary.
Switch Replacement
A bad switch in a microwave can cause various problems, particularly affecting the power supply to the microwave's components. Microwaves are equipped with several internal thermal switches and interlock switches designed to safeguard users in case of component failure. For instance, door interlock switches prevent the microwave from operating when the door is open to prevent exposure to harmful radiation. Additionally, many microwaves feature a magnetron thermal switch that triggers if it detects excessive current or high temperatures in the microwave cavity. Another thermal switch monitors the cooking cavity temperature and activates if it detects high temperatures. If any of these switches fail, the microwave will not function properly; lights, fans, and the display may not work. Due to the inherent risk associated with microwaves containing high-voltage components like transformers and capacitors, which can retain dangerous levels of electricity even when unplugged, it's recommended to have a Sears Home Services professional inspect and repair the microwave.
What to expect when you experience a microwave will not heat up issue
How to fix a microwave that won't heat up
Addressing most issues where the microwave fails to heat typically requires replacing the thermostat, electronic control board, or switch. However, given the numerous potential causes, a comprehensive diagnosis is crucial for resolving the problem effectively. An accurate diagnosis is vital for determining the extent of the repair needed.
Sears Home Services advice for a microwave that won't heat up
When the microwave fails to heat up, several factors could be at play. To prevent unnecessary part replacements, we advise having a Sears Home Services professional conduct diagnostic tests to pinpoint the underlying issue. Our technicians possess extensive experience in diagnosing various microwave failures.
What to watch out for with a microwave won't heat up diagnosis
Identifying issues with modern appliances can be challenging without the right expertise. Attempting repairs without proper diagnostic methods often leads to guesswork part replacements. Over the past decade, appliances have evolved significantly, incorporating intricate electronic components that are hard to assess. Consequently, DIY repairs on newer appliance models are becoming progressively more complex.
Microwave Runs but Does Not Heat Up
Check the control settings when your Microwave runs but does not heat up. Make sure that the heat setting is set to high or the heat setting that you need to cook the item in the microwave.
If the heat setting is okay, try resetting the electronic control board in the microwave by following these steps:
- Stop the microwave if it’s running.
- Unplug the microwave power cord to completely disconnect electrical power.
- Leave the microwave unplugged for 2 minutes.
- Plug the power cord back into the electrical outlet to restore power and reboot the electronic control board.
After resetting the control board, the microwave may work properly. If not a blown fuse, faulty control board, bad safety thermostat switch or wiring failure may be the cause of the problem when your microwave runs but does not heat up.
Schedule microwave repair service to have a Sears Home Services technician visit your home and fix the problem.
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Michael C offered an excellent service
5 stars!!! Michael was quick and knowledgeable! Very accommodating and professional
Andreina G, Naples, FL
microwave
Mark really went over the microwave trying to fix it, this was his second time here for the same problem. August till ? till we get it replaced. we appreciate him for his knowledge of his job. thank you Mark
H M, Cadiz, OH
Customer
Mr. David is very polite and intelligent gentlemen. He came to replace a part on my microwave and he checked the microwave to make sure it was working properly. Mr. David gave me a courtesy call that he will be arriving in 15mins. He arrived on time for the appointment and took care of his job duties. Thanks Mr. David for all the hard work you do at Sears. Keep up all the good work.
Pamela W, Baltimore, MD
Frequently Asked Questions
Repair Microwave Resources
Discover the top causes of microwave malfunctions in 2025 with Sears Home Services.
Find out how magnetrons work in microwave ovens to cook food.
Learn how a convection microwave oven works and how to maintain it.
Is it worth repairing a microwave? Find out the pros and cons of repairing your microwave at Sears Home Services.
Glossary Terms
A microwave diode is an electrical component that allows current to flow in one direction only, playing a crucial role in converting incoming electrical power into the microwave energy that cooks the food.
A microwave sensor is a technologically advanced feature in modern microwave ovens that measures vapor (steam) emitted by the food, adjusting the cooking time and power levels automatically for optimal results.
A microwave waveguide cover is a small, often mica or plastic piece inside the microwave that covers the opening where microwaves enter the cooking chamber, protecting the microwave's internal components from food splatter and ensuring efficient distribution of the microwaves.
A microwave magnetron is a component in microwave ovens that generates the microwaves used to cook food.