Microwave Making Noises? (Top 5 Reasons Why)

Microwave ovens are one of the most commonly used home appliances. If your microwave is making strange noises, it is most likely because a part needs replacing due to such heavy usage. However, before replacing any parts, see if either turning the microwave off and on at the power source or cleaning the microwave solves the noise issue.

The noise your microwave is making and where it is coming from will help you find out what the issue is. A grinding sound from inside the microwave indicates it is the stirrer motor, while a grinding or clicking noise from the base of the microwave indicates it is the turntable. A high pitch or loud hum points to the magnetron or diode, while a rattling or buzzing sound from the rear of the microwave indicates the cooling fan is at fault.

Before repairing a microwave, be aware that it can be very dangerous.

Exercise Extreme Caution

The high-voltage capacitor inside the microwave can store a lethal amount of electricity, even after the microwave has been disconnected from the power for months. To safely access electrical components in the microwave, the capacitor must be discharged. You should be very confident you know what you are doing and are protected from electrocution before discharging the capacitor.

Due to the risk of electrocution, it is recommended that a trained microwave professional be used to repair the more complex issues.

1. Faulty Magnetron

The microwave’s magnetron is responsible for producing the high-frequency electromagnetic waves that cook the food. When you run your microwave on a low setting, you can often hear the magnetron switching on and off to reduce the microwave frequencies while cooking the food. If the noise your microwave is making sounds like the magnetron except louder, it suggests that a faulty magnetron (or diode – see below) is to blame.

A faulty magnetron can also cause an annoying high-pitched sound, which indicates that the magnetron tube is failing due to age and heavy usage.

You can further diagnose a magnetron issue by running the microwave on a low setting and seeing if the microwave noise reduces or stops as the magnetron turns on and off while cooking at the low setting. A burning smell also indicates a problem with the magnetron.

Follow these steps to diagnose and fix a faulty magnetron:

  1. Unplug the microwave from the power source.
  2. Remove the top microwave cover to access the magnetron.
  3. Discharge the capacitor.
  4. Use a multimeter to test the magnetron for continuity. Each reading should be less than one ohm.
  5. If defective, remove and replace the magnetron.

Always exercise caution when accessing the magnetron.

2. Faulty Diode

The diode is a part of the high-voltage circuit, along with the magnetron and capacitor. It converts alternating current to direct current to produce the high voltage needed to power the magnetron. A faulty diode typically makes a loud humming noise.

Follow these steps to diagnose and fix a faulty diode:

  1. Make sure the microwave is unplugged from the power source.
  2. Remove the top microwave cover to access the diode.
  3. Discharge the capacitor.
  4. Use a multimeter to test the diode for resistance. Depending on the model, a healthy diode will read between 50,000 and 200,000 ohms.
  5. Check for continuity in the opposite direction by reversing the meter leads. There should only be continuity in one direction.
  6. If the diode is defective, it will need to be replaced.

Always exercise caution when accessing the diode.

3. Faulty Cooling Fan

A problem with the cooling fan is another reason for microwave noise. Sometimes the cooling fan becomes dislodged or debris gets caught in it. This could be causing the fan to clip against another part of the microwave or be causing a rattling sound.

The cooling fan motor can also wear out and may need replacing. Typically, you will be able to hear the cooling fan when the microwave is operating normally. However, if that noise becomes louder or the microwave is making a buzzing noise, usually from the rear of the microwave, it indicates a problem with the cooling fan motor.

Accessing the cooling fan may require the removal of other microwave parts. It is recommended that you exercise caution and discharge the capacitor.

Follow these steps to diagnose and fix a faulty cooling fan:

  1. Unplug the microwave from its power source.
  2. Discharge the capacitor.
  3. If necessary, remove any components blocking access to the fan.
  4. Examine the fan to see if it is spinning freely. If the fan is not obstructed but is not spinning freely, it indicates that the fan motor will need to be replaced.
  5. Test the cooling fan motor for continuity with a multimeter. Depending on the model, a working cooling fan motor should read 280 ohms.
  6. If defective, replace the fan motor.

4. Faulty Turntable Motor

Another source of microwave noise is the turntable motor. A faulty turntable motor typically makes a clicking or grinding sound. On most models the turntable motor can be accessed from underneath the microwave. If you cannot access it from underneath, you will need to remove the microwave casing.

Follow these steps to diagnose and fix a faulty turntable motor:

  1. Unplug the microwave from the power source.
  2. Before accessing the turntable motor, remove the turntable plate and support roller from the microwave.
  3. Unscrew the turntable motor panel.
  4. Test the turntable motor for continuity with a multimeter. If there is no continuity, it will need to be replaced.

5. Stirrer Motor

The stirrer motor powers a metal blade that deflects microwave energy throughout the microwave. The stirrer makes sure that food in the microwave is cooked evenly. A faulty stirrer motor typically makes a grinding sound as the motor struggles to keep up.

Follow these steps to diagnose and fix a faulty stirrer motor:

  1. Unplug the microwave from the power.
  2. Access the stirrer motor from inside the microwave cavity, above the turntable plate.
  3. Remove the stirrer motor cover.
  4. Check that the stirrer blade has not become loose and is not damaged. You may be able to disconnect the stirrer motor and run the microwave to see if it still makes noise with the stirrer motor disconnected.
  5. If the stirrer motor is damaged, replace it.
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