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Microwave Ovens Master
Re: Kenmore Microwave blows internal fuse
Is the fuse holder tight?
You shouldn't be able to easily rotate the fuse with a thumb and finger while it's in the holder.
If it's loose, that can cause a fuse to overheat and melt inside.
Is the internal cooling fan running?
When I say internal
cooling fan, I do not mean the hood vent exhaust fan which you can turn
on and off manually.
I'm instead talking
about the internal fan which comes on automatically whenever you
The high voltage transformer may be failing.
This is usually accompanied by an electrical smell, but it may be slight enough that the cooling fan disperses it.
You can temporarily disconnect the fan and run it for about a minute (no longer - the magnetron will overheat) and then see if you can detect smoke or smell.
Be sure the loose connector is taped off so it doesn't contact any connections or get hit by a fan, etc.
should be a "mini-manual" (tech sheet) hidden inside the unit
control panel or hidden on the left side behind the grille, which is
very helpful when troubleshooting, testing, and locating components.
You can find
exploded views and order parts by entering your model number at the Sears
But Sears parts can usually be obtained for far lesshere by entering either the part or model number.
Here are some links you
or someone you know can use (in order given) for test help, but read
the safety warnings first:
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Yes, if it really is operating the magnetron and generating microwaves, but that is "virtually" (nearly; almost) impossible, because all microwave ovens come with a special door switch (called a monitor switch) whose job it is to cause the internal fuse to blow and kill power to the microwave. It is more likely that just the fan and light stay on, but not the magnetron, and that is caused by a different defective door switch. (All microwave ovens come with 3 or 4 door switches, and they all must work right for your microwave oven to operate.) You better call a professional repairman to have that microwave checked & repaired.
If it is tripping the breaker when you just close the door, I think it might be one of the door switches that the latch activates. There are usually 3 switches behind the latch holes in the microwave. One is a safety monitor switch that is suppose to blow the internal fuse if the microwave is started and the door is not closed properly. It should blow the micro fuse before the house breaker unless you have a weak house breaker. It will do the same thing if start is pressed and it senses a problem with the door. You say the problem is intermittent so I assume you do get it to work at times so I'm guessing most of the microwave is OK. I'm pretty sure you have a door switch problem--- either out of adjustment ---or 1 of them going bad.
the problem your are experiencing with your microwave oven is a failed interlock switch. Be careful when closing your microwave door. Slamming the door too hard is one of the main reasons that the interlock switch is damaged.
Slamming the microwave door shut can easily blow the microwave fuse, but they can also blow due to problems with the interlock switches. A microwave oven will not function until the fuse is replaced.
Instruction on how to replace fuse on microwave.
1. Unplug the microwave from the electrical outlet to prevent electrocution. Place the microwave in a well-lit area to be able to locate the fuse.
2. Use a screwdriver to remove the outer cabinet of the microwave, and follow the power cord to the fuse. The fuse is located 2 to 3 inches within the microwave and is attached to the power board.
3. Observe the fuse to determine if it is blown. Blown glass fuses will produce burn marks on nearby surfaces, or the internal fuse wire will be black and melted, while ceramic fuses show no outward appearance of being blown.
4. Determine if a ceramic fuse is blown by testing it with an ohmmeter. If the ohmmeter reads zero ohms, your fuse is not blown. Other readings on the ohmmeter show that your fuse is blown.
5. Replace the blown fuse by popping it out of its holder, and snapping a new fuse in its place. Tighten the fuse clips by squeezing them together with your fingers.
6. Replace the outer cabinet of the microwave, and plug the microwave back into the electrical outlet. Test the microwave to see if it's working properly.
If the fuse isn't the problem, check the door hooks and the door-release button. When these are broken, the door switch doesn't activate, so the oven can't work. You should check the internal door switches, the high voltage circuitry and the circuit board for this kind of problems. But for that you will need a certified technician to help you make these repairs.
Hi and welcome to FixYa, I am Kelly.
You have a bad door interlock switch or bent switch actuation arm. Should someone open the door while the microwave is operating without pressing pause/stop when the unit has this symptom will cause the internal fuse to blow and it will not operate until the fuse is replaced. The switches are inexpensive but takes someone with some reasonable mechanical skills and knowledge of using a meter to isolate which of the 3 door interlock switches is causing the problem.
Thanks for choosing FixYa,
does the fuse in the plug blow or the internal fuse if it blows the internal fuse it could be one of the door switches two of the switches have a red button on them and one has an orange button its normally the orange one thats at fault
Usually, when your microwave oven doesn't work it all, the internal fuse (thermal fuse) is blown. This fuse protects both you and the oven. When it blows, you need to have a qualified appliance repair technician replace it.
If the fuse isn't the problem, check the door hooks and the door-release button. When these are broken, the door switch doesn't activate, so the oven can't work.
SWITCHES ARE THERE FOR A PURPOSE-----SAFETY,,SAFETY...ALWAYS CHECK A MICROWAVE WITH THE POWER CORD REMOVED---YOUR MESSIN WITH A RF VOLTAGE THAT WILL KILL YOU!!!! UNPLUG,,UNPLUG,,,UNPLUG
TRY TO CHECK THE FOLLOWING...SINCE YOU HAVE THE COVER OFF,,LOOK AT THE DOOR LATCHES WHEN YOU CLOSE THE DOOR AND MAKE SURE THEY MAKE CONTACT ON THE DOOR SWITCHES,,3 OF THEM,,,--AN OHM METER IS THE TRICK FOR THIS - SOMETIMES YOU CAN SEE PLASTIC BROKEN ON THE SWITCH ITSELF...ALSO LOOK AT THE COMPLETE SWITCH HARNESS (CHECK FOR BROKEN PLASTIC PIECES) THAT HOLD THE SAFETY SWITCHES...THE MIDDLE SWITCH (MONITOR SWITCH) CLOSES WHEN YOU "OPEN" THE DOOR,,YES "OPEN "THE DOOR AND IT WILL BLOW THE MAIN FUSE..IF IT'S SHORTED.
THERMAL PROTECTORS RARELY GO BAD--IF YOU HAVE A PROBLEM WHERE IT TAKES 25 MINUTES TO COOK A BAKE" POTATOE"--JUST LIKE THE VICE PRESIDENT--THAT'S A THERMAL PROTECTOR..
PLEASE BE CAREFULLLLLL TUNICA
I've had this problem twice with our microwave. The hint to where the problem lies is that the breaker blows when you open the door at times. Inside the microwave are three microswitches; primary and secondary interlock micro switches and an Interlock Monitor switch. The switches are supposed to shut down the microwave if it is running and the door is opened. But, I've found the upper primary switch can stick internal at times and when the door is opened the stuck switch will, because of the way it is wired as a safety switch, cause either the fuse or possibly the main circuit breaker for the oven to pop. The reason the stuck switch blows the breaker or fuse is when the door is opened the interlock switch will cause the neutral wire from the AC power to be applied to the Upper Primary Interlock switch which normally should be open when the door is opened, but if the switch is intermittent or the contacts weld themselves shut the neutral line is connected direct to the "hot" side of the power line through the fuse and thermostat. The first time my microwave failed the switch had melted the contacts together inside the switch and the second time the switch became intermittent and would blow the breaker to the over ever so often. I suspected the switch the second time this happened and utilizing an ohm meter I checked the switch several times by opening and closing the door and once in a while it would remain closed instead of opening when the door was opened. Of course while trouble shooting the power cord to the microwave must be disconnected and use all safety precautions when working around the high voltage areas inside the microwave. I wrote Jenn-Air about the bad switch and the way it is wired into the circuit, but never received any acknowledgement. I suspect these microswitches are under rated for the amount of current that passes through the switch, thus they overheat and eventually arc the contacts together. I hope this helps explain the intermittent problem and could explain many of the intermittent blown fuse problems I see in these internet help sessions