Samsung Microwave Not Heating? (here’s why & how to fix)

A microwave is a great addition to any kitchen, using a microwave helps you to cook and heat up your favourite foods in a short time. That is until they stop working as they should.

One of the most common complaints about microwaves is that they stop heating. If you own a Samsung microwave that’s not heating, keep reading. 

In this article we take a close look at all of the reasons why your Samsung microwave might not heat and offer solutions to these issues.

Why Is My Samsung Microwave Not Heating?

There are a number of reasons why your Samsung microwave might have stopped heating which include;

Probable CauseSolution
Demo Mode SelectedClear the demo mode
Kitchen Timer SelectedSelect a normal cooking cycle
Door Switch IssuesCheck that the door is fully closed and the sensor and door switch are functioning correctly
Inadequate VentilationEnsure the vents are clear
Defective DiodeCheck and replace the diode if necessary
Burnt Out Magnetron Check and replace the magnetron if necessary
Burnt Out High Voltage CapacitorCheck and replace the capacitor if necessary
Faulty TransformerCheck and replace the transformer
Blown Thermal FuseReplace the thermal fuse

Let’s take a closer look at each of these issues;

Demo Mode Selected

If your Samsung microwave is in demo mode, all of the buttons and functions will work, but it won’t heat anything. This is because when the microwave is in demo mode it doesn’t use the magnetron.

You can easily tell if your microwave is in demo mode. All you need to do is set a cooking time and start the appliance in the usual way. If it is in demo mode, the timer will count down way faster than usual.

You can clear the demo mode function (which is designed for use in showrooms) by going to the Options or My Settings button. Demo mode is option 6 in the menu.

Setting it to option 2 will turn it off, if your model doesn’t have an Options or My Settings button, consult your user manual for specific instructions.

However, if your microwave timer is counting down faster than usual and your user manual doesn’t mention demo mode, contact Samsung directly for more information.

Kitchen Timer Selected


Samsung microwaves have a kitchen timer option that works just as a timer. If you have accidentally selected this option, the microwave will not heat up.

Always ensure you select the correct option on your microwave, specifically one of the normal cooking cycles.

Door Switch Issues

Microwaves are harmful to humans which is why the doors on microwaves are so secure. The appliance will not start to heat food unless the door is fully closed.

Check the doorway for any dirt or debris that could be preventing the door from closing properly on your microwave. Then check that the door latch and strike plate are aligned correctly.

If you are sure the door is fully closed, the problem could be with the door sensor or door switch. You will need to contact a technician to investigate and repair this fault for you.

Inadequate Ventilation

Unless there is adequate ventilation, your microwave won’t heat properly or operate correctly. If there is inadequate ventilation it will cause the microwave to overheat, which in turn, will cause the appliance to shut down.

This is almost always caused by a malfunctioning vent which becomes stuck with food or other debris. Or, in some cases, becomes damaged due to old age and wear and tear.

You will need to inspect the vents and clean them, as well as ensuring there is sufficient space around your microwave to allow hot air to escape.

Defective Diode


The diode in your Samsung microwave, turns the alternating current (AC) that comes into the microwave via the transformer into direct current (DC).

This doubles the voltage which is what’s needed to power the magnetron and produce microwaves. If the diode develops a fault, it will prevent your microwave from producing any microwaves which means it will not heat up.

This is definitely a job for a technician to investigate and replace the diode if necessary.

Burnt Out Magnetron 

The magnetron produces the microwaves used to cook your food. Running the appliance without any food inside or with the turntable removed can cause the magnetron to overheat and eventually burn out.

Over time, the magnetron could also burn out due to old age and wear and tear. If the magnetron is burnt out you will need to get it replaced by a technician.

Burnt Out High Voltage Capacitor

The high voltage capacitor works with the high voltage diode to increase the power needed for the magnetron to function correctly. If the high voltage capacitor burns out, the microwave will possibly still run, but it won’t heat up.

This is definitely a job best left to a technician because these capacitors are filled with gas and liable to explode if not handled correctly.

Faulty Transformer

If you can smell burning when the microwave is running and there’s a loud humming sound, it’s probably because the transformer is faulty. This is potentially dangerous because of the threat of electrocution.

We recommend contacting a technician to check and replace the transformer if necessary.

Blown Thermal Fuse

Your Samsung microwave has a safety device called a thermal fuse that will cut power to the appliance in the event of it overheating. Once the temperature breaches a predetermined level, the thermal fuse blows preventing any damage to the internal components.

Once the thermal fuse blows, it cannot be repaired, it needs to be replaced. In some appliances, the thermal fuse is an easy fix, however, when it comes to microwaves, we recommend getting a technician to replace the thermal fuse.

This is because it involves dismantling the appliance and exposing areas that can hold a high voltage charge even after the power has been disconnected.

SEE ALSO: Flatbed Microwave Vs Turntable – which is better?

Frequently Asked Questions

Why is my Samsung microwave running but not heating?

If your Samsung microwave is running but not heating it could be because; the demo mode has been selected, the kitchen timer has been selected, there is a problem with the door, the diode is defective, the magnetron is burnt out, the high voltage capacitor is burnt out, the transformer is defective or the thermal fuse has blown.

Why is my Samsung microwave turning on but not heating?

If your Samsung microwave is turning on but not heating it is most probably caused by the demo mode having been activated or the kitchen timer mode has been selected, or you have selected a cook cycle with too low a level of heat.

Is it worth fixing a microwave that won’t heat?

Whether it is worth fixing a microwave that won’t heat depends on the age of the appliance and the cost of repair. If the microwave is 5 years old or less and the repair costs less than half the cost of a new appliance, it is probably worth it.

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