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I have a Kenmore 401.80094700 microwave and today it was heating as soon as the door was closed. Having once worked on appliances I did not think this was possible. We pulled it apart and check all the door switches and they appeared to be ok. It appears that the 120 feed to the HV transformer traced back to two relays on the main circuit board. I know it was heating as butter was melting and sizzling. It did not sound like the microwave cooling fan was running. After checking the switches we plugged it back in and everything appeared to be normal. Does anyone have any experience with this problem and can you tell me what to do? I am kind of afraid to leave it unattended and plugged in at this point. I know the heat sensors on the tube should go out and shut down before there are major issues but I would rather have no issues at all.
Thanks Sam
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Sam, I have GE, model JES 1339WC, that did the same thing in the past and is doing it again. Shut the door and the magnetron turns on, light and turntable do not turn on. The first time it happened, it burned out the magnetron. I was able to get a replacement on еВау for $18. While I had it apart I used the enclosed technical data sheet to trace the 110 voltage to a relay that I suspected of being stuck shut, possibly having spot welded itself. Unfortunately, I can't remember what exactly I did to remedy to situation, but I'm sure it involved testing the relay for open or shut condition with the power off, and testing the voltage through the relay to the disconnected transformer low voltage leads with power on and door open and closed. Finding nothing amiss, I reconnected the transformer low voltage leads, plugged the power cord in and closed the door and the magnetron did not come on. I reassembled the case an it worked fine. I still don't know exactly what I did to fix it.
Whatever it was that I did, I have to do it again, because after 6 or 8 months of proper operation, it started doing it again after heating something for 30 minutes at half power. The cycle finished and the unit beeped to signal it was done. The heating was done to sterilized a liquid, so I was in no hurry to remove it and let it stay on the unit while I worked on something else. After a few minutes the magnetron came on, but the lights and turntable did not. The humming was faint and at first I paid it no mind, being intent on whatever it was I was doing, but after a bit I realized what it must be and went over to check. Sure enough it was the magnetron blasting away at the liquid inside which had boiled over. So I have to disassemble the unit once more and check everything again. I will post any findings. Perhaps it will benefit you or someone else Googling this condition, which is how I found your post.
Jack
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Rank: Member
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After taking the unit apart, the problem was the same as the last time: A power relay carrying current to the hi voltage transformer feeding the magnetron got stuck in the shut position. Opening the door is supposed to open this relay. I can't recall what brought this on the last time, but this time it was after a 30 minute cook cycle at half power and I am guessing that the relay welded itself shut at some point when it closed and hi temp spark melted the contacts just enough to create a metallic bond strong enough to resist the spring trying to push it open. I unsoldered the relay from the board and tested it again and it was still closed. At some point I thought that a sharp rap on a hard surface might break whatever bond was keeping it closed and that's exactly what happened. I resoldered the relay and reassembled the unit and it's working fine. If it happens again it's a matter of removing 5 screws and rapping the relay with a screw driver until I can track down a suitable replacement. The relay in this unit looks like this: http://au.element14.com/.../standard/1891709-40.jpgHope this helps someone. Jack
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Thanks Jack, I replaced the main control board which contains most of the relays and controls. This part with shipping was less than 85.00 so it was worth the peace of mind that it would come on and damage the machine.j
I do appreciate your comments but was afraid to leave the machine plugged in until I had a peace that it was functioning properly.
Thanks for responding.
Sam
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Rank: Member
Groups: Registered
Joined: 6/3/2013(UTC)
Posts: 4
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No problem, Sam. If you replaced the board you definitely solved the problem. When I googled this condition I came across your post and about 5 or 6 others with the exact same symptoms, but no replies to any of them. I count count the number of times I have been steered in the exact right direction to solve an electronic/automotive/mechanical problem. Hopefully this will help someone in the future.
Jack
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