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How Microwave Ovens Work


It isn't magic that pops your popcorn or reheats your lukewarm coffee. It's high-frequency electromagnetic radiation. Microwave ovens generate this radiation in the form of microwaves, using this process:

1. A transformer boosts the normal household current — 120 volts AC — to about 4,000 volts DC.

2. The transformer supplies this beefed-up energy to an electronic tube called a magnetron, which in turn converts the energy into microwaves.

3. The microwave energy travels along a metal conduit called a wave guide, into the interior metal cooking chamber of your microwave oven.

4. A fan-like device called a stirrer, located at the top of the oven, disperses the microwaves evenly as they leave the wave guide.

5. The metal interior of the cooking chamber reflects the microwaves (they can't penetrate metal), agitating the water molecules in the food or liquid inside. The resulting friction generates heat, which quickly cooks or heats that frozen entree or coffee.

6. A fan sucks up the heat from the cooking chamber and cools the magnetron.

Safety and Use

Because microwave ovens produce radiation that can harm you if you are directly exposed to it, today's ovens must meet strict safety standards and are designed to prevent significant leakage of microwave energy. For example, a tight door seal and a metal screen over the glass window on the oven door prevent harmful energy from escaping; a system of locks keeps the oven from operating if the door latch is open.

But just to be safe, take these additional measures to protect yourself and your oven.

  • Call in the professionals. A broken or damaged microwave oven is more than an inconvenience — it's a potential hazard. If you have problems with your oven, call a service technician. By design, the ovens are difficult for a layperson to disassemble, and you may render the oven unsafe (voiding your warranty) if you tamper with it yourself.

  • Follow instructions. Follow the owner's manual for recommended operating procedures and safety precautions for your model.

  • Don't overheat. Don't excessively heat food or liquids, especially in sealed containers; if not properly ventilated, they can burn you or explode. Periodically stir or turn items to avoid hot spots that uneven cooking can create.

  • Don't run an empty microwave. You could ruin the magnetron.

  • Don't use metal. Don't use metal items or foil in your microwave, unless intended for that purpose. Metal reflects microwave energy and can create a magnetic charge that can damage the magnetron or disperse the energy into the air. Use only microwave-safe products (usually indicated on the packaging or the product itself).

  • Watch your door. Keep door seals clean. Never operate a microwave oven when the door is broken, warped, bent or won't close tightly, or if there's any chance the oven will continue to run with the door open.
Copyright 2009, Sears Brands, LLC. All Rights Reserved.
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Recent comments

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Hi Brian. Then you must have a weak fan motor or something within the fan shroud. I recommend you have a service provider come out to check your microwave. There are no user serviceable items within the microwave.

Question from Manage My Home on 11/13/2009 at 1:46pm
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Hi Richard. There are no consumer serviceable parts in a microwave. You can contact a service provider to find out what a service call will cost to compare it to the price of a new one to decided which way you want to go.

Question from Manage My Home on 11/10/2009 at 5:38pm
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I have a whirlpool over range microwave that gives off a humming sound when operating light or fan. It does not make the sound if the door is open.

Question from Brian Hartman on 11/10/2009 at 1:20pm
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My 7-year-old Kenmore Elite microwave model 665.61683101 has stopped heating but shows no error code. I assume the magnetron has failed, and am wondering whether to replace that part or buy a new microwave (is another part likely to fail soon?).

Question from Richard Defouw on 11/05/2009 at 3:21pm
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Hi Val. Some models require you to microwave first, then brown while others let you set the control to operate both types of cooking within one setting of the cycle. You can use the make and model numbers to locate your Owner's Manual on ManageMyHome.com.

Question from Manage My Home on 10/21/2009 at 5:16pm
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I have a microwave with convection cability.....How do i cook steak or bread in it? When the coils in the top heated up to "orange".... i turned it off.

Question from val jones on 10/19/2009 at 8:45pm
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Hi Leslie. The F2 error code means the oven thermistor is shorted or the control board is shorted in the thermistor circuit. I recommend a qualified service provider service your microwave due to the risk of electrical shock.

Question from Manage My Home on 09/25/2009 at 5:25pm
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I have a microwave (Kenmore) older model (#565-68420790), all of a sudden it 's like the breaker popped, no power what so ever. I have tried about eveything and it is still inoperative! What should I do to try and fix it? Thanks, Mr. Joubert

Question from Arthur Joubert on 09/25/2009 at 2:32pm
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What does the error code "F2" mean on a Sears Microwave Speed Oven?

Question from Leslie Kefauver on 09/22/2009 at 2:50pm
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My Kenmore Microwave Speed Oven beeps and displays the message "Error F2." What does that mean?

Question from Leslie Kefauver on 09/22/2009 at 2:49pm
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My Sears Kenmore Microwave (Speedcook Oven) beeps and flashes a visual signal that says "Error F2." What does that mean?

Question from Leslie Kefauver on 09/22/2009 at 2:47pm
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Hi Gene. The error code says this is a humidity sensor failure. You can unplug the microwave for a couple minutes and see if that clears the code and the microwave works again. If it errors out again, you should have a service provider check it out.

Question from Manage My Home on 09/16/2009 at 11:12am
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I am receiving the error -F3H- on my Kenmore Elite model 665-61684 when I try to do most functions with it. In addition the lights and fan are not working. Strange that some options still work. Can anyone shed any light on what this error means?

Question from Gene on 09/08/2009 at 10:12pm
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Hi Virginia. Most models use the F9 error code to indicate a problem with the door lock circuit. This problem could be caused by a loose wire in the lock circuit or it could be a defective control. To know for sure, you'll need a techinician to check it.

Question from Manage My Home on 09/04/2009 at 1:56pm
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Kenmore Elite Microwave won't work, shows F 9 in the window. Should I have repaired or replaced? 6 yrs. old.

Question from Virginia Hall on 09/01/2009 at 9:34pm
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I have a 6 yr old Kenmore Elite over the stove Microwave that won't heat. F9 appears in the window. Is this serious, expensive? Should I just replace it?

Question from Virginia Hall on 09/01/2009 at 9:32pm
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I have a 6 yr old over the stove Kenmore Elite Microwave. It runs but won't heat, F 9 appears in the window. Is this serious? Should I just get a new one or have repaired?

Question from Virginia Hall on 09/01/2009 at 9:29pm
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Hi Art. Most microwaves have a thermal fuse in the top of the cabinet area, but because microwaves operate with VERY HIGH VOLTAGE, they should only be opened by a qualified service technician. I recommend you call one to diagnose and repair the problem.

Question from Manage My Home on 09/01/2009 at 4:50pm
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Overheated a Barbecue on my Microhood and Barbecue caught fire inside. Smoke all over the Kitchen. Microhood is dead nothing works at all. But everything works in the Kicthen. I suspect its the fuse on the Microhood. Where is this located at.

Question from Art Basco on 08/30/2009 at 12:36am

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