Question about Microwave Ovens

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I have a Magic Chef MCO160UQ over the range microwave. It started by tripping the braker. I would turn the breaker back up and it would work, after a week doing that, it stopped working. first, I thought I had a faulty breaker so I went and buy one and replaced, but the microwave kept tripping it. I searched around this website, repairClinic, and other websites for solutions. I didn't find anything specific, but just a couple of troubleshooting tips such as testing the thermal fuse and the line fuse. I opened it and tested the thermal fuse and it had continuity, and I tested the line fuse 20a250v and it didn't. I replaced the line fuse, connected it and it worked, I was so happy. I placed it back up over the range, set time up. Once I open the microwave door, there it goes again...I was not happy. It turned off, shut completely down and tripped the breaker. I turned the breaker back up and the microwave shows the time, but I wont touch it anymore until I find out that is causing this. then I'll take it down and repair it. Please let me know what part is acting up or sending this purge of electricity that is even tripping my breaker. I am sure I can replace the part, please let me know what I need to do... man, I tell you, I guess I never thought how dependent we were from this thing to heat up mostly everything... thanks, Look forward hearing from you. Fabricio D.

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Hello there and welcome to fixya
this has been a fairly common issue with these over the counter or stove microwave
The problem normaly stems from the power inverter that is shorting out causing the breakers to trip so what i would do is first take out the poower inverter and have it tested ok now keep in mind that you wil wnat some continuity but not a lot so if your reading is fairly high then replace the part here is some more stuff that will need to be tested ok
A defective relay can result in a variety of symptoms: * A relay with its contacts welded (stuck) closed would result in the oven coming on as soon as the door is closed or the power being stuck on high no matter what the touchpad setting. * A relay that doesn't close (due to defective contacts or a bad coil) would result in no heat and possibly other things like the fan and turntable not working as well. If the relay is totally inoperative, test for voltage to the coil. If the voltage is correct, the relay may have an open coil. If the voltage is low or zero, the coil may be shorted or the driving circuit may be defective. If the relay makes a normal switching sound but does not correctly control its output connections, the contacts may be corroded, dirty, worn, welded closed, binding, or there may be other mechanical problems. Remove the relay from the circuit (if possible) and measure the coil resistance. Compare your reading with the marked or specified value and/or compare with a known working relay of the same type. An open coil is obviously defective but sometimes the break is right at the terminal connections and can be repaired easily. If you can gain access by removing the cover, a visual examination will confirm this. If the resistance is too low, some of the windings are probably shorted. This will result in overheating as well as no or erratic operation. Replacement will be required. The resistance of closed contacts on a relay that is in good condition should be very low - probably below the measurable limits on a typical multimeter - a few milliohms. If you measure significant or erratic resistance for the closed contacts as the relay is switched or if very gentle tapping results in erratic resistance changes, the contacts are probably dirty, corroded, or worn. If you can get at the contacts, the use of contact cleaner first and a piece of paper pulled back and forth through the closed contacts may help. Superfine sandpaper may be used as a last resort but this is only a short term fix. The relay will most likely need to be replaced if as in this case the contacts are switching any substantial power.

Posted on Feb 10, 2012

  • 3 more comments 
  • Fab Feb 11, 2012

    which one is the power inverter? Also, you mentioned the power inverter and then you start talking about a relay? and how I need to test it? it;s all in greek to me?
    by the way, the last long paragraph, I noticed you copy/paste it from repairfaq.org but whatever,
    i guess I was expecting a more simple explanation to trouble shoot it.
    the only part I understood was to take the power inverter out, but I guess I assumed you were going to tell me which one it is and how to take it out and how to test it? or is this asking to much for $8 dlls?
    excuse my ignorance about the subject, but please, if you can help me out with a little bit more detail about which one its the power inverter and how to test it. wehn I told you i tested te thermal fuse for continuity, I learned those terms in a youtube video, and made sense to it, but I am dumb on this stuff... please help me with more details steps? please like a 10 yr. old. thank I dont mean to be a pain in the rear...

  • Fab Feb 20, 2012

    I didn't understand his response at first, so I asked him again about the specific part he refers to the power converter, but he has not responded. i guess I just wanted a simpler response from him. the same way he copied and pasted how to troubleshoot, I guess he could have copied pasted a diagram of the parts so I identify the part he is refering to. That is all I need. If that was his final answer, then i am not happy with the service and I need a refund or maybe a better explanation on how to resolve my problem. thanks

  • Michael Thomas
    Michael Thomas Feb 21, 2012

    Hello there again and than you for the reply iam sorry that i didnt break it down a little bit more for you but yes i can
    i used the repair clinic blog because it explains it and allows you to see a video at the bottom of there page on testing parts i would like to send you a pict of the power invertser and other parts but ill have to send them to a e-mail fixya wont let me post picts here in the comment section ok i can send them to you and i will hav e the full dissassembly instructions to go with it ok this should help you out in explaining each of the parts and how to remove them and test them ok
    sorry i didnt explain it earlier and no you are not a pain in the rear lol this is what i am here for is to help you

  • Fab Feb 24, 2012

    no problem. Thanks. Please send everything to my email at
    Please send them AS SOON AS you can....they're killing me here that they don't have a microwave, we've been without a microwave for a month. thanks

  • Fab Mar 07, 2012

    hello, anything Mr. Thomas, I've been waiting for your answer for a month. Can you please assist me? you said you will email me the solution and you have not sent anything. you can not handle all your clients, please let me get the solution from somebody else, but I need a solution, I've been waiting with out a microwave and you know what that means in our fastpace culture, I am going through very challenging times, having to warm my stuff in other ways. Please responde ASAP, I am getting really frustrated now.



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