Top 20 Emerson MW8987B/W Microwave Oven Questions & Answers

Generally, the most common causes of a failure to heat are: - bad door switches or door switch mounts - loose or corroded connection at the magnetron - problem or loose connection on the control unit circuit board - bad magnetron - shorted high voltage diodeSee the following help files on safety & disassembly and door switches.You can find links to helpful exploded view diagrams and part ordering help here. I recommend that you bookmark that link to your favorites. We're happy to help you with free advice and we'd appreciate your thoughtful rating of our answer.

Unfortuneately the keypad control board must be replaced to resolve this issue. But keep in mind the part alone is more expensive than some microwave ovens.

The keypad control board is the likely problem, but the door switches should be checked first.

If the door is not closing, the door latch is broken at the tip, or inner mechanism, or the door is out ot of position and not lining up.

Hello,

Investigate these three areas if your microwave won't heat up foods.

Power Diode

A diode is an electronic component that readily passes current in one direction only and blocks the flow of current in the opposing direction. If your microwave's diode has become defective, your microwave will not heat. Test the diode to determine if this is the cause of your problem. Replace it if it is defective.

Testing a diode

NOTE: Before you test your diode, make sure your microwave is unplugged, and that you discharge the microwave's capacitor.

Whether it is shorted or open, a defective diode will most likely show some sign of defect. Defective diodes will usually emit an electrical burning smell, signifying its defectiveness. Also, it may have split in two, or it may exhibit a burned crack, or possibly even a blistered spot.

A shorted diode is indicated by a loud humming noise from the high voltage transformer, and no heat produced when a cook cycle is initiated. Whereas little or no heat produced in your microwave, with an absence of a humming noise is indicative of an open diode. In either case, the diode has to be replaced.

With your microwave unplugged, and your capacitor discharged, use extreme caution to remove the lead that leads to the capacitor. You can leave the ground connection attached. The side of the diode that goes to the ground is usually marked with a dot, stripe, or arrow. Set your ohmmeter to R x 10,000 or higher. Touch the positive meter probe to the anode and the negative meter probe to the cathode to measure the resistance across the diode terminals. Remember that the cathode is on the side that goes to the ground, which is often marked by a dot, stripe, or an arrow.

A normal diode, that is a non-defective diode, will read anywhere from 50,000 to 200,000 ohms. Differences in microwave make and model account for this large range in resistance readings.

Reverse the meter probes and measure resistance while touching the positive probe to the cathode and the negative probe to the anode. Reversing the probes like this should result in a reading of infinity. Unless a bleeder resistor is present. The presence of a bleeder resistor would produce a reading of the value of the resistor.

High Voltage Capacitor

A capacitor is an electrical device which stores electricity. A defective capacitor may be why your microwave is not heating. The capacitor will have to be tested to determine if this is the cause of your problem. A defective capacitor will have to be replaced before your microwave will work again. Make sure you discharge the capacitor before you test it, though.

Magnetron

A defective magnetron is the third possible cause of why your microwave is not heating. Test your microwave's magnetron. Replace it if it is defective.

Testing a magnetron

NOTE: Before you test this component, make sure your microwave is unplugged, and that you have discharged the capacitor.

There are two tests to conduct in order to determine whether or not a magnetron has become defective. If you receive results other than what are detailed below, you will have to replace your microwave's magnetron. Each test is described for you here:

TEST 1: Locate your magnetron and label each of the wires attached to it so that you know which wires are to be replaced where. Set your ohmmeter to the lowest resistance scale. Take a resistance measurement between each of the magnetron terminals by touching each probe to one terminal each. Reverse the probes and take a second resistance measurement. Each measurement should read less than one ohm.

TEST 2: Set your ohmmeter to its highest resistance scale. Touch one of the meter's probes to a magnetron terminal. Touch the other probe to the metal magnetron housing. Take special caution to not touch the two probes together. This could result in an inaccurate reading. This test should produce a reading of infinity - indicating an open circuit.

If you cannot perform the above task yourself, ask a family or friend that has the ability to assist you or have a certified and experienced appliance repair technician examine and replace your magnetron. This task is much too dangerous for the average layman to perform on his own.

Read the tips on the below links on how to replace your microwave oven's diode and how to discharge the capacitor.

http://www.fixya.com/support/r7088355-replace_microwave_ovens_diode

http://www.fixya.com/support/r7088317-discharge_microwave_ovens_capacitor

I hope the above is helpful.

Regards.
Walesarumi

You can find links to helpful exploded view diagrams and part ordering help here. I recommend that you bookmark that link to your favorites.

First of all, thank you very much for choosing FIXYA today for your online technical support needs. I'm Joe, and I will be more than happy to assist you with your service request. Here is a direct link to the ONLINE USER'S MANUAL for an Emerson 8993 model which has all the same features as yours and will have identical operating instructions:http://www.emersonelectronics.ca/emerson/documents/MW8993WC%20-%2009%20cu%20ft%20Touch%20Control%20Microwave%20Oven%20with%20Omni%20Wave%20CookingBilingual.pdf To view the Owner's Manual with Operating Instructions just use your mouse to click on the link, which is the underlined and blue highlighted text just above. This will open a new web browser page automatically for you and allow you to view the information at the website indicated and the contents of the Owner's Manual. You may need ADOBE READER installed on your computer to read PDF documents, although many computers already have this utility pre-installed. You can always download this for free at WWW.ADOBE.COM if necessary. Click on the DOWNLOAD ADOBE READER button on right side of the ADOBE home page when you get there, then follow the onscreen instructions to install the software on your computer. Please COMMENT back here to this page if you have any details to add, have any questions, have difficulty accessing the links, or just require further general assistance and I will respond as soon as I see it. If you were satisfied with the service provided, could you please take a moment to leave a 5 STAR rating. Your feedback is very important and I truly appreciate your consideration. BEFORE leaving a rating OTHER THAN 5 STARS or a negative TESTIMONIAL, please contact me and I will immediately clear up any concerns or answer any additional questions that you might have until you are completely satisfied with the service provided. The FixYa rating system is a very important component of the Marketplace, and unfortunately once you post a rating or a testimonial to a solution, it cannot be changed at all later on. Be sure to use the small blue ADD A COMMENT button located just below the text of this solution to leave any additional comments for me regarding this particular issue and I will respond right away. I truly hope that was helpful to you. Good luck and take care. Joe.

Hi,
Here is a tip that will help you to figure out what is wrong with yourMicrowave Oven....

Microwave Oven Basic Troubleshooting Tips

heatman101 ,/.';
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Hi,
Here is a tip that will help you to figure out what is wrong with yourMicrowave Oven....

Microwave Oven Basic Troubleshooting Tips

heatman101

Could be one of a few things. if everything works but no heating of food.there is a fuse from the magnetron transformer to the big capacitor check if it is blown. If everything works but the sound is just different ,almost lower in pitch check the diode from the capacitor to the metal casing ,, it \normally goes short circuit.Then if all is good, very likely to be your magnetron. Magnetons are expensive .

Open the unit. On top where mains come in would be a big fuse normally 10amp , its blown. This is almost always caused by faulty door switches. Also check diode from the big cap to earth. be careful the cap can store high voltages even when unit is off.Discharge capacitor first with a wire to earth.Make sure the unit is off.The fuse will also blow if that diode is blown.they usually go short circuit.

It sounds like the magnetron may have either failed or is not being supplied with the extremely high voltage required to run it.

YOUR SAFETY IS PARAMOUNT

This is a job for a professional but if you are safety clued up, here's instruction.
Make sure the !!!!capacitor is discharged!!!!! before attempting any sort of repair.
Check the door interlock switches first then the high voltage diode with either an AVO model 8 or moving coil meter on high resistance range for short circuit, (DVM's won't show the fault!), the capacitor can fail and go short circuit, the feed fuse on the primary of the high voltage transformer and then finally, the magnetron is best checked by substitution.
Hope that helps.

Load test.

A simple safety test.
Place 1/2 litre of water in a glass container. Measure the temperature of the water.
Place in microwave and heat on full power for 1minute.
Measure the temperature after it has stood for 1minute.
If the temperature difference is more than 9 degrees Celcuis the magnetron is working and producing about 700Watts of heat.
If your microwave is labelled with 900 or 1000Watts. That is about right.
If the temperature is less then the magnetron is not working properly and may need replacing.

This a only a rough guide and any doubts you should consult an authorised service agent.

Hi,

Here is a tip that will help you to figure out what is wrong with your Microwave Oven....Microwave Oven Basic Troubleshooting Tipsheatman101

Hi,

Here is a tip that will help you to figure out what is wrong with your Microwave Oven....

Microwave Oven Basic Troubleshooting Tips

heatman101

Definitely sounds like a defect or misadjusted door switch. This site has venders of M/W parts. FYI,Federal law requires a leakage test after door repair, magnetron replacement or interlock repair.

it is behind the control panel but easy to get to if you remove the metal skin from the whole microwave (3 Screws)

I can tell you what we did when we had that issue with our Maytag microwave. The door wouldn’t latch correctly and an appliance repairman said we would have to get a new microwave. My husband took the spring out and decided to just put the spring back. It had come unhooked somehow. He put it back and it’s worked fine going on 3 years later.

it maybe the internal fuse tht has blown all microwaves have a monitor fuse inside some where the mains power comes in and some on the control pcb it does mean that a short circuit has accured but it can happen if the door is slammed you will need to remove the top cover of the unit to find the fuse and be very careful inside everything is very sharp and door make sure it is unpluged also inside a microwave i a large capacitor this can store power even with the unit off it should be grounded b4 working on the unit but a long as you are just changing the fuse you should ok do if you can use insulated pliers for your own safety,if u fit a new fuse and it blows again thn my advise would be to take it to a a repair shop as the high voltage side of your microwave is up to 4000-5000 volts

Look inside. Any access panel?

Remove the cover to find the lamp. dont touch the silver can. unplug the machine before you open the case.

Appliance Parts Pros web-site,if they dont have it they will find it for you.....great $$$$ and fast shipping