Tip & How-To about Microwave Ovens

Microwave oven Troubleshooting

Just about all MW ovens made in the last 15 years are almost identical inside and operate in a similar manner. Most have a service sheet packed inside that will contain basic troubleshooting tips. If your having trouble with your oven, first remove the top and sides cover. It will be secured with security TORX screws. Now slide cover toward the rear.
First, does the interior light and control panel display come on? If not check the 20amp slow blow fuse located near where the power cord enters the cabinet. If bad,replace.
Next if the oven gives every indication that it is cooking yet does not actually heat your food, then check for 110V at the large power transformer. If no voltage than check the three micro-switches that are part of the door latch interlock. Failure of one of these switches is very common.
If the 110V is present and yet unit does not cook and/or unit makes a loud vibrating noise, then the problem could be the magnetron, diode, or capacitor. WARNING: There is over 2000V in this circuit. Even when unplugged the capacitor could still hold a charge. Discharge cap by using a screwdriver and short across the two terminals. There is an internal bleeder that should take care of this but discharge the cap just to be sure. The diode can be checked by using a 9 volt battery to bias the diode on. Note: The diode function on your multimeter can not be used in this instance. The Capacitor can be checked by using an ohmmeter seeing if you see a surge as the cap charges. Reverse leads to check again. There isn't an easy way to check the Magnetron but arcing in the cabinet and/or a very loud buzzing are indications that one has failed. Mags are not normally replaced due to cost, about $75.

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WILL NOT SHUT OFF, LIGHTS UP, TURNTABLE RUNS, MAKES NOISE, ONLY WAY TO SHUT OFF IS TO PULL PLUG OR OPEN DOOR


This is a classic door switch problem. I fixed a friend's MW a few months ago that had this exact symptom. Got a family member's MW going again last summer for similar (not identical) problem.

In our case, one of the switches was broken (shorted). There are usually a group of similar door switches all mechanically ganged together behind the latch. If the MW has a wiring diagram, you can use it to figure out which switch controls the light, fan and turntable. Check the switch with ohm-meter after you get it out. The switch plunger may have lost it's springiness.

You need to be clever mechanically to figure out how to disassemble for the R&R (remove&replace). Don't break plastic mounting pin or you may have to improvise repair for that too!. It may help to have the service manual for your particular model (worth a google search). The switch is probably relatively inexpensive ($5 or so) and a generic replacement should work fine if it has the same-or-higher voltage and current rating.

Apr 22, 2016 | Microwave Ovens

1 Answer

I have LG model number LMS1271SS. I bought it 1and half year back from Sears. For the last one month the plate inside the micro wave has stopped revolving. Pls let me know how can I fix it.


The turntable may have a belt that is broken or sliped off, some models may have a motor for this and it may be dead. Most microwaves have a service sheet folded up inside, remove the outer cover and look around. Unplug the MW before going inside. Replace the outer cover before testing your repairs.

Apr 08, 2011 | Microwave Ovens

1 Answer

neff microwave combination oven


no solution sorry but we also have a Neff mw/combi oven which keeps blowing for no apparent reason, the Neff repair man has looked at it 4 times and practically replaced every component -power module, operating module,relay board, door switches but it`s just gone again! The model is a H5972N0GB/01 and it is approx 3 yrs old, no problem for the first 2 years .Time to write to Neff -is yours the same model?

Apr 23, 2008 | Microwave Ovens

1 Answer

Neff HTHB86K Microwave oven.


The microwave unit is faulty as you can read from the display or the controller isn't working correctly, you should take your MW oven to an authorized service center. It can be repaired by yourself but it's highly dangerous because it has high voltage inside and microwave energy.

Feb 15, 2008 | Microwave Ovens

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