Question about LG Microwave Ovens

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Erm microwave lg mc804a has started to overheat and shutdown cleaned all the vents from dust etc now its got 2 fans 1 near the main transformer and the other at the backend on the microwave the 1 at the back of the microw blade is mental shouldnt that be turning when the microwave is running ?

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The cooling fans must be working and vents clear to ensure good cooling air flow.

Otherwise, the magnetron will overheat and it will shut down.

If this continues too long, the magnetron will be damaged.

We're happy to help and we appreciate your thoughtful rating of our answer.

Posted on Jun 29, 2008

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Emerson microwave mwg9115sl over heats then turns back on after 20 minutes


Your magnetron is overheating, which can be caused by:


  • operating oven without cover(s) in place
  • wrong magnetron installed in oven
  • an old or otherwise failing magnetron
  • cracked magnetron magnet
  • improper power line voltage (should be 110-125VAC)
  • foods low in moisture (popcorn & bacon, e.g. - add 1/2 cup of water in rear oven)
  • failed or inoperable cooling fan or hood vent exhaust fan
  • deteriorating foam weatherstripping seals in air ducts or on outside cover
  • blocked air vents (dust, animal nest debris, insufficient free air space behind & around oven, etc.)
  • clogged or greasy charcoal filter or grease filter
  • blocked duct in hood vent exhaust

The first suspects in my book are fan failure, blocked vents, or bad magnetron.

Jan 10, 2013 | Emerson Microwave Ovens

1 Answer

Microwave stops working when heating food


Foods that are low in density or low in moisture (such as bacon and popcorn, respectively) can cause the magnetron to overheat.

That's because there is not enough of either mass or moisture to absorb enough of the microwave energy put out by the oven.

The excess energy then reflects back to the magnetron and causes a standing wave (like a poorly tuned transmitter antenna) and causes the magnetron to overload and overheat.

When the mag gets too hot, it trips the magnetron thermostat, a protective device which rests when it cools.

If this overheating is a persistent problem, a stopgap is to put about 1/3 to 1/2 a cup of water in a microwave-safe container (a Pyrex measuring cup is ideal) in a REAR CORNER of the microwave whenever you cook such items. This will help absorb excess energy, but you may have to increase cooking time just a little.

And of course I always suggest that food items be placed off-center in the microwave, NOT in the center of the turntable, otherwise the food is not exposed evenly enough to the microwave energy and will not heat as efficiently as it could.

(Placing it in the center is sort of like stirring paint by twirling a stick in the center instead of pulling it around in a circle in the paint can).

Such inefficient heating wastes the energy at best, and at worst it puts a strain on the magnetron.

If a magnetron is repeatedly subjected to such stress, it will prematurely fail. It will also draw excessive current, which can strain the high-voltage transformer.

That in turn will often lead to the oven's drawing excessive current, resulting in a hot cord and plug, and the fuse will blow - hopefully before the transformer or magnetron does!

An overheating magnetron can be due to:

  • operating oven without cover(s) in place
  • wrong magnetron installed in oven
  • an old or otherwise failing magnetron
  • cracked magnetron magnet
  • improper power line voltage (should be 110-125VAC)
  • foods low in moisture (popcorn & bacon, e.g. - add 1/2 cup of water in rear oven)
  • failed or inoperable cooling fan or hood vent exhaust fan
  • deteriorating foam weatherstripping seals in air ducts or on outside cover
  • blocked air vents (dust, animal nest debris, insufficient free air space behind & around oven, etc.)
  • clogged or greasy charcoal filter or grease filter
  • blocked duct in hood vent exhaust

Jan 07, 2013 | Danby Designer Series DMW111KPSSDD

1 Answer

Model mmv1163dw00 had put frozen veggies in for 15 minutes, when done it beeped and then it went dead. I unplugged, tested my outlet which was okay. waited about and hour and plugged in and it worked. Can...


Yes, there is a thermostat on the magnetron that detects when it overheats.

When it does, it will shut down power until it cools back down.

This protects the magnetron from the destruction posed by overheating, which can be caused by:
  • operating oven without cover(s) in place
  • wrong magnetron installed in oven
  • an old or otherwise failing magnetron
  • cracked magnetron magnet
  • improper power line voltage (should be 110-125VAC)
  • foods low in moisture (popcorn & bacon, e.g. - add 1/2 cup of water in rear oven)
  • failed or inoperable cooling fan or hood vent exhaust fan
  • deteriorating foam weatherstripping seals in air ducts or on outside cover
  • blocked air vents (dust, animal nest debris, insufficient free air space behind & around oven, etc.)
  • clogged or greasy charcoal filter or grease filter
  • blocked duct in hood vent exhaust
Check as many of these these things as you can and correct as necessary.

You can find helpful exploded view diagrams and order parts by entering your full model number here.

Let us know if we can help further.

We're happy to help you with free advice and we'd appreciate your thoughtful rating of our answer.

Aug 21, 2010 | Maytag MMV1163DS Stainless Steel 1000...

1 Answer

We have a model # mmv1153bas over the range microwave. When heating or cooking items longer than a couple minutes the unit shuts off and remains off for at least 1 hour. It is not the breaker or the plug...


If it goes dead for a while during or after cooking then comes back on, the magnetron is probably overheating and causing the magnetron thermostat to open.

Then when it cools, it closes the circuit and allows power through again.

An overheating magnetron can be due to:
  • operating oven without cover(s) in place
  • wrong magnetron installed in oven
  • an old or otherwise failing magnetron
  • cracked magnetron magnet
  • improper power line voltage (should be 110-125VAC)
  • foods low in moisture (popcorn & bacon, e.g. - add 1/2 cup of water in rear oven)
  • failed or inoperable cooling fan or hood vent exhaust fan
  • deteriorating foam weatherstripping seals in air ducts or on outside cover
  • blocked air vents (dust, animal nest debris, insufficient free air space behind & around oven, etc.)
  • clogged or greasy charcoal filter or grease filter
  • blocked duct in hood vent exhaust
We have a sound clip of what a microwave should sound like when the cooling fan and high voltage section are operating here.

It is vital that the cooling fan runs, or the magnetron will be destroyed. Repeated shutdowns like this are endangering the magnetron, assuming it's not bad already.

Your owner's manual will cover checking the filters and will cover warranty terms. The magnetron may still be covered.

If for some reason you don't have your manual, you can download it here.

We're happy to help you with free advice and we'd appreciate your thoughtful rating of our answer.

William E. Miller
prototech@usa.net
http://www.microwavedisplay.com

May 25, 2010 | Maytag UMV1152BAS Microwave Oven

1 Answer

My microwave stops goes dead after running for 2 minutes


It may be that the magnetron is overheating. The main causes:

- blocked air vents
- blocked air outlet or duct (if an over the range type)
- clogged grease filters needing to be cleaned
- clogged charcoal filter needing to be replaced
- failed internal cooling fan
- failing magnetron

Depending on the model, it may have a thermostat on the magnetron so that the power is killed if it overheats, then it comes back on when it cools down.

We have a sound clip of what a microwave should sound like when the cooling fan and high voltage section are operating here.

Please listen to that and compare it to yours. You may hear that your cooling fan is not 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 microwave.

It is vital that the cooling fan runs, or the turntable and stirrer won't work, and magnetron will soon be destroyed.

If instead the microwave starts microwaving then it scrambles and then comes back up as if someone unplugged it for a couple of seconds and you can set the clock and start again, then you have a magnetron that is leaky.

Once you listen to that and check your vents, filters, etc., let us know what you find so we can take it from there.

Please note that FixYa is not currently notifying us Experts when Clarification Requests are answered.

To allow us to help you effectively (at no charge), please post a
NEW problem to FixYa, and please include your brand name and the full model number from the tag in or on the unit, and your detailed symptoms, as well as the results of these recommended checks.

Dec 12, 2009 | Samsung Microwave Ovens

1 Answer

First of all, my do it yourself expertise is very high. I have power to the microwave (panel, interior light, etc). When I try to operate the microwave - the electronic panel intications are normal, but...


BECAREFUL high voltage transformer inside of unit. Check for blown fuses on the control panel. Check the door interlock sitches. there are usually 2-3. A bad interlock will keep power from the magnatron. Check the thermal fuse, small dime sized disc with 2 wires. look for the schematic it will give the location usually near the magnatron. Checking the magnatron is a little more difficult.

Oct 10, 2009 | Whirlpool MH7140XF Microwave Oven

1 Answer

Microwave lights and buttons work but doesn't heat up anything


When you start the microwave say for 1 minute. Listen closely when you hit start, the light should come on and about a 1/2 second later you should hear a little click and a slight hum. This means the controller is turning on the high voltage transformer and that part of it is working. My guess is that the magnatron is bad. That's the most common problems with all brands of microwaves. The mat on the top should not have caused the problem since the microwave has heat shutdowns in it. I would say that it's a 90% chance it's the magnatron. Most microwaves have a 5 year warranty on that part. Look at your owners manual. Good luck.

Scott

Jan 23, 2009 | Amana Radarange Microwave Oven

1 Answer

Thermador model CM302UB displays error F34 when microwave is in use for morwe than 2 minutes


There are two main possibilities. The first is that the main circuit boards in the oven are not being properly cooled. The second is that there arere are some components that have become thermo sensitive, and are acting with heat.

Check to make sure that the vent fan is working properly. Check to see if the vent hole in the rear of the oven is clogged with a lot of dust. If there is dust, clean it out.

Jerry G.

May 14, 2008 | Thermador Microwave Ovens

1 Answer

LG LMVM2055SB over the range microwave keys not working


Is it possible someone may have sprayed cleaner directly onto the keypad area?

This causes moisture to get into the keypad and sometimes onto the control board.

This could mean that they control panel frame with keypad (membrane switch) would need to be replaced.

Can you give more details on the cleaning?

Nov 18, 2007 | Microwave Ovens

1 Answer

Fan?


It may be that the high-voltage transformer or magnetron has failed and is loading down the voltage. The presence of smoke usually indicates a bad transformer.

 

I would try a toaster or toaster oven in that outlet to see if it works right. That's a good line load test.

 

If you don't feel good air flow, it can overheat and ruin the magnetron.

 

If you or a friend decide to work on it, we have *critical* safety, disassembly, and troubleshooting info at our site, which is linked at our listing here on FixYa: http://tinyurl.com/yzjozk

Aug 28, 2007 | LG LMV1650ST Microwave Oven

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