Replacing Your Microwave’s Diodes: How to Diagnose Microwave Not Cooking Issues

Appliance Express
August 30, 2017
Microwave Repair

Sometimes microwaves don’t break down completely as a result of a blown fuse or a busted transformer. Instead, sometimes your microwave can carry on the passive functions of lighting up, telling time, and even rotating the turntable inside without actually heating up your food. In these circumstances, something is interfering with your microwaves ability to fully utilize its power.

If you have a Frigidaire Gallery FGMV174KFB (2012), you can test the functionality of each of these parts with a multimeter. There are three parts of your microwave that deal primarily with the high voltage side of things and connect to your inline fuse: the capacitor, the transformer, and the magnetron. You can test the rectifiers, or diodes, of your magnetron, which are responsible for converting electricity from AC to DC.

You can test each of the three components of your broken microwave in the order that is most convenient to you and you feel the safest doing; capacitors and diodes are the most common causes of problems, and you want to be sure you are handling the electrical parts safely.


The Procedure for Testing the Diode, or Rectifier, of Your Magnetron:

Get a nine-volt battery and insert the readers of your voltmeter as a standard. Then use gator clips to put the diode in a series circuit with the battery to test the voltage. A diode or rectifier should cause a voltage drop, in this circumstance one of approximately 3 volts. If you read the same voltage as the battery, then the diode is bad and needs to be replaced.

You can test a new diode with the same procedure of creating a series circuit and confirm that there is an appropriate drop in voltage. Rectifiers can fail, so it is a common cause of microwave and appliance malfunction.

Installing Your New Diode: 5304467670

Be sure the cathode side is on the ground and the anode side is on the capacitor. It’s extremely important to connect the diode in the correct direction to ensure a safe, functioning connection. The negative side of your rectifier will typically have a band around the nearest edge of the of the middle component in order to denote which side it’s on; it will also have a ground connector, which looks like a circle on the end of the wire. The positive side won’t have a band and will have a bit that goes to the capacitor.  The negative side is the cathode side, and the positive side is the anode side. Make sure you keep those different sides straight!

Other Potential Electrical Problems with Your Microwave:

If your diode is working and doesn’t need to be replaced, the next best component to test is your capacitor, and then the high-voltage side of your transformer. Transformers can be a little tricky to test because the high-voltage side can be broken while the low-voltage terminals are perfectly operational. On this part, look for blackened pieces or signs of smoke. The high-voltage winding to ground connection should also have a resistance of zero ohms, and if it doesn’t you’ve found your broken component.

As always when you taking apart and replacing parts in an electrical appliance, take care to reattach the parts exactly as you found them and to use insulated tools. If you will be working on or near the microwave’s capacitor, take the extra step of manually discharging it instead of hoping the voltage will dissipate if you wait ten to thirty minutes. And if you want to learn more about repairing your own microwave and major appliances, check out Appliance Express for more articles and product-specific tutorials.


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