4 Common Microwave Problems and Fixes

There are 4 common microwave breakdown problems;

  • Your control panel may not be working
  • There is excessive noise from your microwave
  • Your microwave is not heating food properly and
  • Your microwave door will not lock

Below are the possible fixes for these problems before calling out an engineer;

Broken control panel on microwave 

If your microwave’s control panel is not working, there are some basic fixes you can run to establish whether it is broken. First, clean the panel may not be responding because it may not be detecting your fingers. Use a damp cloth to wipe down the control panel, dry it and then test again.

Next, check for control panel lock controls. Some microwaves have a control lock. If this is enabled, the other buttons will be unresponsive.

There are also cases when some buttons will not respond while other functions are being used on the microwave. See your user manual for details about control lock and when the button you are trying to use may not respond. Finally, try resetting the microwave by unplugging it for one minute.

Another possible cause of certain microwave buttons or the whole control panel not working could be an issue with the membrane switch. This membrane is more commonly known as the touchpad. It has a few soft-touch electrical switches. There is a certain conductive coating on the touchpad which can go defective with repeated usage. To check this issue and to resolve it, you will need to unplug the appliance and remove the cabinet. Check the membrane switch using a multimeter for continuity. When buttons are pressed, the multimeter should pick up on a few ohms of electrical resistance. If there is a reading of zero ohms (zero resistance) replacement will probably be in order.

Another possible reason for the control panel failing to work could be an issue with the control board. If the touchpad of your appliance is unresponsive but the display lights are still showing, then this could be the issue. The control board is responsible for generating a low voltage which is in turn supplied to the membrane switch.  In case the control board does not generate a low voltage signal then you may need to replace it.  Replacement of the control board should only really be attempted by a professional. It involves disconnecting the microwave from the main power supply and then taking apart the cabinet, replacing the unit, and then reassembly.

If you are able to detect the problem accurately and feel confident about your knowledge and skill with household electrical items, the replacements can be made with a trained repair specialist. While this will save you money it is not advised for amateurs to try replacing microwave parts on their own, perhaps contacting your appliance insurance provider will be the best option.

Microwave breakdown and fixes

Excessive noise from microwave

If your microwave is making an unusual or loud humming noise, there may be a problem with the magnetron. This component is part of the high voltage circuit and provides the microwaves that generate the heat. If the magnetron is not working as it should, it may cause a loud humming or buzzing noise.

To have a look at your microwave’s magnetron you will need to locate the unit using your manufacturer’s manual. It will then require removal of the cabinet. Disconnect the power and discharge the high voltage capacitor to prevent an electrical shock. You can then locate the magnetron and disconnect the two attached wires and the mounting screws to remove it. You should also check the high voltage diode to verify that the circuit has not shorted before writing off the health of your magnetron.

An alternative problem may be with the drive coupler for the turn tray. Most microwave ovens with a round glass tray use a motor-driven coupler to rotate the tray. Some models that use a rectangular tray will have a drive coupler that has an offset centre roller to drive the tray guide from side to side. For each, remove the tray and roller guide from the oven and then inspect the coupler. Some may require removal of motor from the bottom before the coupler can be removed from the motor. The coupler usually has an opening that fits tightly onto the motor shaft. If it is damaged it may become noisy and will need to be replaced. Also, when removal of the bottom cover is required first, disconnect electrical supply first.

Should your microwave be making an unusual or too much noise when the turn tray is rotating, the problem may be with the roller guide under the tray. Some microwave ovens with a round glass tray use a motor-driven coupler to turn the roller guide. The roller guide is used to support the tray and to engage the rotating coupler. Remove the tray and then inspect the roller guide. Check the hub to see if it engages the coupler securely and the outer rollers for signs of damage. If there appears to be damaged, replacement is necessary. Other kinds of microwaves may only rely on the roller guide to support the tray however it may be these wheels which are damaged resulting in an unusual noise. If the roller guide appears to be normal, then check the coupler for damage.

Microwave not heating food properly

If your microwave is failing to heat your items, quite possibly the magnetron is broken. Regrettably, a fried magnetron is beyond repair. A replacement will be needed. Other issues include a broken diode or a faulty door switch. We’ll come to those later.

To determine if the magnetron is at fault, disconnect the electrical supply and discharge the high voltage capacitor to prevent an electrical shock. You may need to consult the manufacturer’s diagrams to find the exact location of these components. Find the magnetron and disconnect the two attached wires. Connect the wires from a multi-meter to the magnetron terminals and check for continuity. There should be only two to three ohms of resistance between these terminals. If there is no continuity, then the magnetron is finished and requires replacement. Also, use the multimeter to check for continuity between both terminals and the grounded outer case of the magnetron. If there is any continuity between either of the terminals and ground, the magnetron will need to be replaced. If these continuity tests do not reveal these defects, then live voltage tests could be necessary. Please refer to a qualified repair specialist.

The second possible reason for why your microwave oven does heat, maybe a problem with the high voltage diode or rectifier. This supplies the all-important high voltage to the magnetron. To look at its state, access will require removal of the protective enclosure. Refer to your manufacturer’s diagrams – it found near the high voltage capacitor. Disconnect the power and discharge the high voltage capacitor to prevent an electrical shock. You can then test the diode for continuity with a multi-meter. Diodes are polarity specific. Low resistance should be found with the meter leads in one direction and higher resistance when the meter leads are reversed. Most multi-meters will have a special setting for diodes or rectifiers. If the high voltage diode shows low resistance in both directions or shows no continuity, then a replacement will be needed. If you find the high voltage diode tests pass, then we need to see if power is being supplied to the circuit or not. This is a high voltage circuit and further testing should only be performed by someone qualified, perhaps an engineer from your microwave insurance provider.

The final reason may be a problem with a door switch. These are sometimes referred to as interlock switches. They provide power to the various components in the microwave when the door is in a closed position, and interrupt power when the door is open. Sometimes it is possible that when an interlock switch fails, the fan motor and or stirrer motor may continue to operate but the magnetron will not. These switches are found inside the cabinet and are activated by hooks or latches on the door. Unplug the unit and unscrew the cabinet. The interlock switches will have wires attached to the terminals marked common (C) and often open (NO). Check the switches for continuity using a multi-meter. With the actuator button pressed, there should be continuity between these terminals. If there is no continuity the switch will require replacement. Closely inspect and verify whether the interlock hooks fully engage the switch actuator when the door is closed. Adjustment of these hooks is possible and necessary for the microwave to work as it should. If you cannot bend these hooks slightly, replacement of the entire microwave appliance is essential.

Microwave door would not lock

If your microwave door fails to latch or is not closing, it may be because of a broken torsion spring. This is an easy problem to diagnose and repair yourself. Torsion springs are used to keep the microwave door closed on units with doors that open downwards.

To inspect microwave torsion springs, disconnect your microwave. Most microwaves will have two springs, one on either side. Begin by removing the door panels to locate the springs, they will be at the bottom of the door. Look at the springs for any signs of wear, corrosion, or damage. If you identify any issues, replacement torsion springs are needed.

Alternatively, the problem could be with the door latch assembly. This often has two hooks which link to the switch holder on the frame of the microwave. When the hooks work as they should, they engage the switches to begin powering the microwave. No latches, no power. The latch assembly is mounted with spring to provide sufficient tension for engagement of the hooks.

To inspect, disconnect your appliance from the power source. Then find and remove the door latch assembly. It will be found behind the inner door panel. Again, look at door latch assembly for any signs of cracking, wear, damage, or discolouration. If you find any of these a replacement door latch assembly is in order.