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Samsung Microwave Not Heating? Here’s Why (+ How To Fix)

A Samsung microwave not heating is a common issue because it has a lot of critical components that can fail over time or suddenly. Also, its customizable settings or functions can cause some errors. So, why is your Samsung microwave not heating, and how do you fix it?  

Here’s why your Samsung microwave is not heating:

  • The microwave is in demo mode.
  • The door isn’t closing or locking.
  • At least one door switch is bad.
  • The settings aren’t accurate.
  • Ventilation is poor or restricted.
  • The cooling fan isn’t running.
  • An internal thermal fuse is blown.
  • The thermoprotector is broken.
  • The high voltage diode is faulty.
  • The microwave capacitor is bad.
  • The oven transformer is dead.
  • The magnetron isn’t working.
  • The control board is defective.
  • The unit has electrical issues.

Some of these issues can be solved quickly and cheaply, but others require delicate inspection. I don’t recommend accessing and testing the high-voltage components unless the necessary safety precautions are in place. Read on to find out why your Samsung microwave is not heating. 

The Microwave Is in Demo Mode

Samsung microwaves have a demo mode that allows users to interact with the controls without the unit heating. So, if you have a new Samsung microwave not heating straight after installation, you should check the demo mode and turn it off. Also, take care not to accidentally turn on the demo mode.

How To Fix

You should deactivate the demo mode. You can find this on “My Settings” or “Options” in most Samsung microwaves. 

Here are the steps to turn off the demo mode in a Samsung microwave:

  1. Press “My Settings” or “Options” on your Samsung microwave.
  2. Watch the display and wait for the Demo Mode option. The Demo Mode option usually appears at 6 for most models, but make sure you double-check yours just in case it shows up as a different number.
  3. Press “6” or the corresponding number for your model. The buttons “1” and “2” should be on and off, respectively.
  4. Press 2 to deactivate a Samsung microwave’s demo mode.

Check your model’s manual if any of these steps don’t apply.

The Door Isn’t Closing or Locking

A Samsung microwave won’t heat if the door doesn’t close completely. The door latch serves as a locking mechanism for the internal circuit to activate. Only then will the unit’s magnetron get the power to generate the microwaves. Otherwise, there’ll be no microwave — and by extension, no heat.

A Samsung microwave door may not close or lock properly for the following reasons:

  • Gunk buildup around the frame
  • A broken door latch or spring
  • Misaligned or deformed door

How To Fix

Inspect the door and ensure it closes perfectly. Also, use the following solutions based on the results of your inspection:

  • Clean the door to eliminate any gunk or crud.
  • Check if the latches are working properly.
  • Replace any broken door latches or springs.
  • Ensure the Samsung microwave is leveled.
  • Inspect and fix any door alignment issues.

At Least One Door Switch Is Bad

A Samsung microwave’s door latches serve as the locking and triggering mechanism. However, they’re not the switches activating and deactivating the electrical circuit inside the appliance. There are door switches inside that can break, and a bad switch can prevent your microwave from heating. 

Most Samsung microwaves have at least two door switches. Your model may have more. These door switches don’t have anything to do with the control panel or display, so you can interact with your microwave or toggle the settings. However, the appliance won’t heat if a switch is bad.

How To Fix

You need to test the door switches and replace a bad one. Here are the steps to do so:

  1. Unplug the Samsung microwave from the wall outlet.
  2. Get a pair of Phillips and Torx screwdrivers. You’ll also need a multimeter or continuity tester.
  3. Remove all the screws for the control panel section. Remove the screws at the top, front, and sides.
  4. Take off the housing panel to access the door switches.
  5. Take a photo of the wires and connectors for reference.
  6. Unplug the wire harnesses and take out the door switches.
  7. Set your multimeter to continuity or least resistance.
  8. Place the probes on the terminals of each door switch.
  9. Press the door switch actuator and check the reading. Multimeters with a beep feature will make a sound. Continuity testers with an LED will glow if the switch works.
  10. Replace a door switch that has no continuity or resistance.

The Settings Aren’t Accurate 

Samsung microwaves have many customizable settings. Some settings don’t work in sync. So, check if any selected settings are preventing your microwave from heating. Some of the typical settings to check are:

  • Kitchen timer
  • Keep warm
  • Power level

The kitchen timer isn’t a cooking or microwaving function. Instead, it keeps time in case you want an alarm or notification when you’re busy in the kitchen. Similarly, the ‘keep warm‘ mode doesn’t heat food. Finally, your selected ‘power level’ determines the heating intensity.

Many Samsung microwaves have the following power levels:

  • 10 – Warm
  • 20 – Low
  • 30 – Defrost
  • 40 – Medium Low
  • 50 – Medium
  • 60 – Simmer
  • 70 – Medium High
  • 80 – Reheat
  • 90 – Saute
  • 100 – High

Also, Samsung microwaves may not heat properly if you overstuff the oven. Likewise, incompatible containers and cookware can affect radiant heating in a microwave. These issues aren’t technically settings, but they can also cause uneven or poor heating.   

How To Fix

Review your settings and fix them. For example, you can:

  • Choose a cooking cycle instead of the kitchen timer.
  • Don’t set it to ‘keep warm’ mode.
  • Select the appropriate power level for optimum heat.
  • Avoid overstuffing the microwave.
  • Use microwave-compatible containers and cookware.

Ventilation Is Poor or Restricted

Samsung microwaves don’t operate effectively or efficiently without sufficient ventilation. A microwave oven can also stop heating if it senses a lack of cooling. Therefore, you must have adequate clearance around the microwave. Overheating is the most common cause of blown thermal fuses and thermistors.

Furthermore, some parts can get charred or burned due to overheating from causes like power surges. So, you should double-check the installation and ensure that your Samsung microwave is well-ventilated.

Additionally, check if the blower is working properly. Even if your Samsung microwave has some space around it and the vents are clear, a malfunctioning blower may not ventilate the unit properly.

How To Fix

Samsung recommends at least 20 cm (approximately 8 inches) of space above their microwaves and 10 cm (approximately 4 inches) on both sides and behind. If you don’t have this clearance, your microwave is likely to have problems. Besides, overheating can damage several parts, forcing you to make expensive repairs.

Inspect the blower motor too. A working ventilator fan should buzz. If you don’t hear a noise when you set the microwave to high heat, you need to check whether the motor is stuck, because a broken blower motor needs to be replaced.  

The Cooling Fan Isn’t Running

Samsung microwaves have a cooling fan next to the control panel to protect the electronics. If this fan isn’t running, your Samsung microwave may not heat. 

Unlike the blower which ventilates your microwave, the cooling fan is similar to the one you have on your desktop computer. This fan doesn’t necessarily make a loud sound, nor should it create the kind of vibration or resonance a blower motor generates. 

So, you may have to take apart the microwave to investigate any issues. Do note that a malfunctioning cooling fan doesn’t necessarily cause the issue. The related electrical components and sensors may be the culprit. 

How To Fix

You can use the same approach as explained in the door switch section above to disassemble the microwave. Most models have the control board behind the front panel with all the buttons and display. You’ll find the cooling fan behind the main control board.

Ensure the microwave is unplugged at the wall outlet before accessing its internal components. Once you have access to the cooling fan, spin its blades manually to see if they rotate. You can also touch the fan motor to check if it’s hot. 

A hot motor or any kind of charring and burning are definitive signs of a broken cooling fan. You must replace therefore it. 

However, if you don’t find anything wrong with the fan, you have to inspect the thermistor that turns its motor on and off. I’ll discuss this further in the thermoprotector section.  

An Internal Thermal Fuse Is Blown

Samsung microwaves have at least one thermal fuse. This thermal fuse protects the control board and electronic components including the sensors. A blown thermal fuse won’t let your microwave heat. 

A thermal fuse may blow due to the following factors:

  • Power surge
  • Overheating
  • Faulty part

The overheating problem could be due to poor ventilation, a broken blower, or a bad cooling fan. So, you can’t limit your inspection to the thermal fuse. The solution has to cover all the broken components based on your findings.  

How To Fix

The solution is replacing a blown thermal fuse. But you should confirm if the thermal fuse is bad first. 

Here are the steps to do so:

  1. Unplug the microwave and follow the disassembly approach explained above in the door switch section.
  2. Locate the thermal fuse after removing the front control panel section.
  3. Remove the thermal fuse and test its continuity with a multimeter or tester. A functioning thermal fuse should have continuity and very little resistance. The resistance reading may be close to 0 ohms but not open-loop or infinite.
  4. Replace your Samsung microwave’s thermal fuse if it fails the continuity test.   

The Thermoprotector Is Broken

Samsung microwaves have a few thermoprotectors. If your microwave’s main thermoprotector fails, the entire heating system won’t work. These thermoprotectors aren’t the same as thermal fuses. A thermoprotector is similar to a thermistor or thermostat. 

A thermal fuse blows only once when it encounters an abnormal surge of electricity or heat. Therefore, you have to replace it to get the microwave to heat again. On the other hand, a thermoprotector resets after disrupting the electrical circuit during overheating and resets when the unit cools.

However, if the thermoprotector is broken, it won’t switch on as you set the microwave to heat. In effect, the main thermoprotector keeps the circuit open, so no electricity flows to the heating system. 

Likewise, a bad cooling fan thermoprotector will fail to prevent the electronics from overheating. This failure can in turn lead to a blown thermal fuse. Alternatively, the main thermoprotector may shut the heat to protect the microwave.

How To Fix

Like thermal fuses, microwave thermoprotectors aren’t usually repairable, so you have to replace this crucial component. Also, a standard continuity test may not work on thermoprotectors at room temperature. These sensors switch on and have continuity in a live circuit due to increasing heat and resistance. 

So, you can’t rely on a continuity tester or multimeter to know if a thermoprotector is bad when it isn’t active in a live circuit. 

However, you can look for signs of damage. For example, a blown or broken thermoprotector may have corroded or charred terminals. You may also find the wire harnesses connected to these thermoprotectors a little burnt. Test the wiring to be sure.

I’m sharing a way to test the wires connected to a thermoprotector. But I don’t recommend this process if you aren’t used to working with electrical components, especially high voltage appliances like microwaves. Don’t try this if you aren’t sure of your skills.

If you are sure of your skills:

  1. Unplug the Samsung microwave and take apart the housing.
  2. Check the main thermoprotector for signs of damage.
  3. Remove the wiring harnesses from the thermoprotector.
  4. Take off the connectors or harnesses and join the wires.
  5. Use electrical tape to temporarily connect the wirings.
  6. Replug the microwave into the wall outlet and turn it on.
  7. Get some water in a microwave-safe cup and place it in.
  8. Set the microwave to quick heat for 30 seconds or so.
  9. Stay away from any exposed and powered magnetrons.
  10. Unplug the microwave and take out the cup of water.
  11. If the water is warm or hot, the thermoprotector is bad.
  12. If the water isn’t warm, something else is broken.

That said, don’t use this testing method of connecting the two wires as a solution, even if it’s temporary. A thermoprotector is a safety fixture, and trying to circumvent it for testing isn’t ideal. 

The High Voltage Diode Is Faulty

Samsung microwaves have a high voltage diode connected to the capacitor. This diode spikes the voltage supplied by the transformer. Also, the high voltage diode converts AC to DC, which is necessary for the magnetron to function. 

If the diode is faulty or goes bad, the magnetron won’t have the high voltage required to emit the microwaves. Therefore, your Samsung microwave won’t heat.

How To Fix

You can test the diode for continuity to check if it’s broken and replace it. However, don’t access the diode or use these tests if you aren’t equipped with insulated gear. Also, it’s safer if you allow a microwave capacitor to discharge overnight before getting anywhere close to it.

Since the diode is connected to the capacitor, you might experience an electrical jolt if the latter has any charge left. Capacitors retain charge for some time after such appliances are off and unplugged. 

Here are the steps to test a high voltage diode in Samsung microwaves:

  1. Use insulated pliers to disconnect the high voltage diode from the capacitor.
  2. Get a multimeter using a 9V battery, since simple continuity testers won’t work.
  3. Test the two terminals of the diode with your multimeter probes for continuity.
  4. Your multimeter should detect continuity from one terminal of the diode to another. However, there should be no continuity if you reverse the probes on the terminals.
  5. If there’s no continuity in either straight or reverse alignments, the diode is bad.
  6. If you find continuity in both directions as you reverse the probes, the diode is bad.
  7. If there’s continuity only from one terminal to another, the high voltage diode is good.

The Microwave Capacitor Is Bad

A bad high voltage capacitor is a common reason for a Samsung microwave not heating. As I’ve said, don’t try to access the capacitor unless it’s fully discharged. You can discharge it, but the methods aren’t the same as you’d use for low voltage capacitors.

If you don’t find visible signs of damage, you might have to test the high voltage capacitor to check if it’s bad. Also, you must make sure the other related parts aren’t the culprit, such as:

  • Diode
  • Magnetron
  • Transformer
  • Control board

How To Fix

Allow the capacitor to discharge at least overnight, if not longer. Alternatively, you can get a 2W resistor rated for 20,000 ohms. 

Here’s how you can safely discharge a Samsung microwave’s high voltage capacitor:

  1. Unplug the microwave and take apart the housing.
  2. Use insulated pliers to disconnect the capacitor’s wires.
  3. Get an insulated screwdriver to disassemble the capacitor.
  4. Place one probe of the 2W, 20K ohms resistor on a terminal.
  5. Use the resistor’s second probe to touch the other terminal.
  6. Hold the probes for a while to discharge the capacitor.

Some high voltage capacitors have three terminals on each set. In these cases, you can use the first probe for the outer terminal and the second for the one in the center. Afterward, you can use the probes to cover the remaining outer terminals, ending with the other central one.

Don’t use a screwdriver to connect two or more terminals to discharge a high voltage capacitor. Also, don’t use the short circuit method of discharging low voltage capacitors because the one in your Samsung microwave may get damaged terminals. 

Likewise, using a typical multimeter or other methods isn’t safe for discharging any high voltage capacitor.  

Once you’ve discharged the high voltage capacitor, test it with a multimeter as follows:

  1. Check the capacitor’s resistance on its chassis. 
  2. Set the multimeter’s resistance setting accordingly.
  3. Place your probes on the terminals of the capacitor. You should get a reading of around the rated resistance.
  4. If you have an analog multimeter, observe the deviation.
  5. Place the probes on the terminals and notice the jump.
  6. Reverse the probes or terminals and observe the spike.
  7. If there’s no spike or reading, the capacitor is bad. 

A good capacitor doesn’t have continuity unless it’s shorted. So, a continuity test is useless. But you can still test a bad capacitor that way. You should also use the probes for one terminal and the chassis of the capacitor to detect a short. If you detect a bad or shorted high voltage capacitor, you should replace it. 

The Oven Transformer Is Dead

A blown transformer usually has visible signs of damage. For instance, the component may be somewhat deformed or arced. Also, the windings may appear burnt. But internal issues can be to blame too. So, you have to test the transformer to be sure of the cause of the issue. 

How To Fix

Don’t access the transformer unless you’ve discharged the capacitor or the latter is unplugged for a long time. That way, you can lose any retained charge. 

A high voltage transformer has three windings:

  • Primary windings (thicker wires)
  • Secondary high voltage winding
  • Secondary low voltage winding

You have to test all the windings and also for shorts. Since there are multiple resistance tests involved in this process, I think a video will be more helpful for you than a series of steps.

Here’s Fred’s Appliance Academy testing a Samsung microwave’s transformer:

Replace your Samsung microwave transformer if it fails any of these tests.

The Magnetron Isn’t Working

The magnetron emits the microwaves inside the oven. If you’ve inspected all the components and issues I’ve listed up to now, your Samsung microwave’s magnetron isn’t working, or the control board is bad. But if the control panel, buttons, or settings work, test the magnetron. 

How To Fix

Ensure the microwave is unplugged and the capacitor is discharged, as explained above.

Here are the steps to test a magnetron:

  1. Dismount the magnetron from the microwave.
  2. Get a multimeter and set it to least resistance.
  3. Touch the terminals with the multimeter probes. The multimeter should detect nominal resistance. No or infinite resistance implies a bad magnetron. 
  4. Set the multimeter to its maximum resistance.
  5. Connect one multimeter probe to either terminal.
  6. Place the other probe on the magnetron’s case. If you get a reading, the magnetron is shorted.
  7. You can use a continuity test to check for a short. Any terminal and case shouldn’t have continuity.
  8. A shorted magnetron is bad, so you have to replace it.

The Control Board Is Defective

If any of the above issues aren’t to blame for your Samsung microwave not heating, you likely have a bad control board, or some wires are fried. Damaged wires should be evident by now after taking apart so many parts.  

How To Fix

A Samsung microwave’s control board has several components, including:

  • Regulator
  • Microcontroller
  • Relays
  • Transistors
  • Switches

You may have a bad relay that regulates the power supply to the heating system, which is the magnetron. Alternatively, the corresponding transistors or tactile switches may also be bad. 

So, replace the control board or a bad part. Otherwise, consult a local technician. 

The Unit Has Electrical Issues

Any significant electrical issue can be the cause of your Samsung microwave not heating. A few probable reasons for that are:

  • Voltage fluctuation
  • Amperage problems
  • Incompatible wiring
  • Bad power cable
  • Surge protector
  • Extension cord
  • Electrical short
  • Broken wires

How To Fix

Samsung doesn’t recommend using extension cords or surge protectors. If you have to use an extension cord, it has to be rated for the same amperage as the wires in the circuit and the power cable. Also, the extension cord or system should be grounded, i.e., a three-pronged plug. 

If you have any significant electrical issues, you should contact a technician to inspect the entire installation.