It can be confusing if your microwave stopped working but still has power. Occasionally, microwaves will appear to function normally without actually heating your food. Often this means that when you start the microwave, the lights will turn on, but you won’t hear the regular noise of a microwave. There are a couple reasons why this might happen. But, be very cautious when it comes to repairing your microwave.

Safety First If Your Microwave Is Not Heating

Microwaves are no joke. You could be seriously injured (or worse) by the amount of high voltage electricity that a microwave contains. It’s common to believe that you’ll be safe by simply unplugging the microwave. However, that is not the case. Even after the microwave is unplugged you can receive a lethal electric shock. The following information might help you understand why your microwave isn’t heating. But, you should call a licensed technician to check for issues and make any repairs. Even opening the microwave’s covering can be extremely dangerous.

Magnetron

The magnetron generates the heat in a microwave. A faulty magnetron can lead to a blown fuse, which may cause further issues to other parts. The magnetron needs to be tested to really know if it is or is not functioning. The following steps help to prevent an electric shock, but can still be dangerous if you’re not a professional.

  1. Unplug the microwave
  2. Remove the covering on the back of the microwave
  3. Discharge the high voltage capacitor

A multimeter can test the magnetron. Disconnect the magnetron’s wires from their current position in the microwave and connect them to the multimeter. If the multimeter isn’t indicating any continuity from the magnetron, then the magnetron should be replaced by a licensed technician. If the magnetron is showing the regular two to three ohms of resistance, then you should consider the following possibilities.

High Voltage Diode

The high voltage diode gives power to the magnetron. If it isn’t functioning properly, the microwave may not be heating. Sometimes a high voltage diode looks visibly burnt out. If that is the case, it may be safe to assume that the diode needs to be replaced. If you can’t draw a conclusion based on the diode’s appearance, a multimeter can test the high voltage diode. Again, the following steps will help avoid an electric shock, but aren’t advised for anyone besides a technician.

  1. Unplug the microwave
  2. Remove the covering on the back of the microwave
  3. Discharge the high voltage capacitor

The multimeter should indicate that one direction of the diode has high resistance and that the other has low resistance. If you see different results, the diode should be replaced.

Door Switch

Microwaves are programmed to only heat when the doors are closed. Door switches indicate when the doors are open or closed. Most microwaves have a few door switches. Before checking the switches a technician will usually:

  1. Unplug the microwave
  2. Remove the covering on the back of the microwave
  3. Discharge the high voltage capacitor

A multimeter is then used to check each door switch for continuity. The door switch actuator button must be pressed while using the multimeter. You can also check on the door hooks which activate the door switches. The hooks could be the problem.

Thermoprotector

The thermoprotector controls how much heat the microwave emits. If the heat rises above a certain level, the thermoprotector will turn the power off. If the thermoprotector isn’t working, the technician may need to reset a tripped fuse.

Consult a Professional If Your Microwave is Not Heating

These are the most common reasons why a microwave won’t heat when it has power. Once again, rely on a licensed technician to make any replacements or repairs concerning your microwave.

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