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Thread: How to fix a broken microwave

  1. #1
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    How to fix a broken microwave

    My cabinet mounted microwave stopped working recently, and after a few searches on Google I figured I would try to fix it myself before calling in the pros.

    *Note - Make sure you unplug or kill the circuit breaker for the appliance before attempting to do any work inside. My wall mounted unit's circuit breaker is part of a dual microwave and oven unit, and the circuit breaker ended up being in the panel outside by my meter instead of in the garage. Once inside, make sure you drain the capacitor because it can still have energy stored in it. DO NOT TOUCH THE METAL POSTS ON THE CAPACITOR WITH YOUR BARE HANDS OR BARE METAL, it'll be a shocking experience!*

    My microwave started doing weird things like not spinning when I tried to heat something up, but would spin very slowly when I opened the door. Google and YouTube kept telling me to check the fuses and door "micro switches". Most microwaves have 2 to 3 micro switches; One tells the microwave that the door is secured and will allow the magnetron to activate, another turns on the light when you open the door, and a 3rd (if it has 3) is a redundant safety switch.

    Click image for larger version. 

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    Micro-switches have 2 modes - Normally Open (NO circuit) and Normally Closed (NC circuit). When the button is not depressed, whichever terminal your wires are connected to determines if it is an open circuit or closed circuit. One door micro switch, for example, would be normally open (NO), because when the door is closed, the button is pressed, turning off the light, and turns it on when you open the door which releases the button the micro switch which turns the light on.

    There are numerous examples and videos available online on how to replace the switches so I won't go into a lot of detail. I found out by opening my Kenmore microwave that it's GE components, typical of Kenmore appliances to just re-badge other manufacturers appliances.

    Replacing the micro switch took me about 15 minutes the first time after figuring out how to open the front panel of my wall mounted unit. Stand alone units are much easier, as the latches and switches are readily accessible simply by removing the metal cover.

    You can order replacement switches from the manufacturer, or other online retailers such as Amazon. I ordered mine from searspartsdirect, and it turned out to be the wrong one (was a NC instead of a NO micro switch), so I went to Amazon and got a 5 pack of universal micro switches that had posts for both NO and NC - https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

    You'll need to ensure that the replacement switch can handle the voltage and amperage of the one you're replacing. Some manufacturers will not sell internal parts to "common folk" and/or say that only qualified electricians should replace parts inside the microwave. While I agree you need to be able to read and operate a screwdriver and maybe pliers pliers to do this repair, it's about as hard as replacing a spark plug in a car.
    Last edited by skindog; September 4th, 2016 at 7:42 AM.
    Common sense is not as common as you'd think...

  2. #2
    Join Date
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    Limiting the repair of a microwave oven that is disconnected from a power source to that of micro-switch is fairly safe.

    Allowing the capacitors to dissipate over 30 minutes or wearing rubber gloves and shorting the caps with a 10K ohm resister is the best method to ensure discharge.

    I would STRONGLY suggest that one not remove the magnetron or attempt to replace it without training.


    In fact, if the magnetron is blown, I would suggest tossing the entire microwave and not attempting a repair at all.

    The outside metal case of the microwave is constructed as a faraday cage, designed to contain the RF (radio frequencies) and prevent energy from escaping to the outside.

    Experts have varying opinions on the safety levels of leaking RF energy from a microwave.

    IMHO - it is not worth the risks associated with exceeding those acceptable RF levels in trying to save a buck by changing out a magnetron and making a mistake.

    To get an idea of how serious RF levels can be in organic material - here is a video of some idiot who actually put a cat in the microwave.

    https://www.youtube.com/watch?v=2T8L1uiK6pE
    Attached Thumbnails Attached Thumbnails MAGNETRON.jpg  

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  4. #3
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    I have replaced more than a few of these micro switches on numerous micro wave ovens, and after the first time it seems so simple that you wonder why more folks don't mess with it.

    It isn't rocket science, and the problem most microwaves have is in the micro switch for the door. When you close the door and hear that loud pop, that is the door latch snapping it closed. That amount of force over a long time simply wears the switch out. Any time you hit something enough times with force, it will stop working... Sort of like why my wife has such a hard time getting me to do anything any more.
    If you do not read the news you are uninformed. If you do you are misinformed. Mark Twain


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