Emerson MW8987B/W Microwave Oven Logo
Posted on Dec 01, 2012
Answered by a Fixya Expert

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It does not heat up

It. Comes on and runs but it. Doesn't cook the food

1 Answer

William Miller

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  • Emerson Master 9,179 Answers
  • Posted on Dec 01, 2012
William Miller
Emerson Master
Level 3:

An expert who has achieved level 3 by getting 1000 points

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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 diode

See 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.

1 Related Answer

Anonymous

  • 43501 Answers
  • Posted on May 08, 2011

SOURCE: How to fix an Emerson microwave 8992RD that

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

Microwave Oven Basic Troubleshooting Tips

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Wolf convection microwave

see the next steps , use the VOM and fix it. God bless you

  1. Check the power diodeThis electronic component is responsible for transmitting current in one direction. If the diode becomes defective it will cause your microwave to not heat. Test the diode and replace it if necessary.
  2. High voltage capacitorResponsible for storing electricity, this part is a key component in any microwave. Remove, discharge, and test the capacitor to determine if it requires replacement.
  3. Damaged magnetronResponsible for generating waves and producing heat. When your microwave is no longer heating properly, replacement will be required.
  4. Thermal CutoffsExamine the thermal cutoffs on both the magnetron and the oven itself. Take off one of the leads and using a volt-ohm meter on RX1, check the terminals. If you get a result other than zero, replace the thermal cutoffs.

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Sharp convection microwave oven model R1875F. It's cooking on the left side faster then the rest of the oven. It seems to burn on the left side and not cook in the middle.

see the next causes. God bless you
Diode The high voltage diode converts the A/C power output of the transformer to D/C, doubling the voltage to nearly 5,000 volts. This high voltage powers the magnetron which emits the energy that cooks the food. If the diode burns out, a lower A/C voltage reaches the magnetron, which is not sufficient to power the magnetron. When the diode fails it is often visibly burned out. If it appears to be good, it can be tested with a volt-Ohm meter capable of testing diodes. High voltage diodes frequently fail and are one of the most common points of failure in a microwave oven.

Door Switch If the microwave does not heat, one of the door switches might be defective. Microwave ovens normally have three door switches, if any of them fail the microwave does not turn on and does not heat. Check the switches for continuity with an Ohm meter.

Magnetron If the microwave oven doesn't heat the magnetron tube might have burned out. The magnetron uses high voltage, high current DC power to generate the microwave frequency that cooks the food. If the microwave oven is turned on when it is empty this can cause the magnetron to burn out. Once it is burned out it has to be replaced, it's not repairable.

High Voltage Capacitor If the microwave doesn't heat the high voltage capacitor might be defective. The high voltage capacitor works with the high voltage diode to convert the output of the transformer to DC voltage and to double the output voltage. If the capacitor is burned out the entire high voltage circuit stops working properly. The high voltage capacitor can be checked with a special VOM meter which has a capacitance testing capability. Be aware that the high voltage capacitor can retain a charge of more than 3,000 volts and can injure or kill a person if not handled properly. Only trained technicians should perform this type of testing.

High Voltage Transformer If the microwave does not heat, the high voltage transformer might be burned out. Microwave ovens produce a very high voltage in order to power the magnetron antenna, which emits the energy that cooks the food.

Thermal Fuse If the microwave doesn't heat the thermal fuse may have blown. It can be tested for continuity. Watch our fuse testing video for more information.

Thermoprotector If the microwave doesn't heat the thermoprotector may have tripped. This is a safety device to prevent the microwave from overheating. It can be tested for continuity to see if it's blown.

Main Control Board If the microwave doesn't heat the main control board may be defective. This is not common. When a microwave doesn't heat the problem is usually within the high voltage circuit; either the high voltage capacitor, diode, transformer or magnetron.
10_4_2012_4_35_53_pm.gif10_4_2012_4_36_18_pm.jpg
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Sharp micro doesn't heat

see this causes and fix it. God bless you
Diode The high voltage diode converts the A/C power output of the transformer to D/C, doubling the voltage to nearly 5,000 volts. This high voltage powers the magnetron which emits the energy that cooks the food. If the diode burns out, a lower A/C voltage reaches the magnetron, which is not sufficient to power the magnetron. When the diode fails it is often visibly burned out. If it appears to be good, it can be tested with a volt-Ohm meter capable of testing diodes. High voltage diodes frequently fail and are one of the most common points of failure in a microwave oven.

Door Switch If the microwave does not heat, one of the door switches might be defective. Microwave ovens normally have three door switches, if any of them fail the microwave does not turn on and does not heat. Check the switches for continuity with an Ohm meter.

Magnetron If the microwave oven doesn't heat the magnetron tube might have burned out. The magnetron uses high voltage, high current DC power to generate the microwave frequency that cooks the food. If the microwave oven is turned on when it is empty this can cause the magnetron to burn out. Once it is burned out it has to be replaced, it's not repairable.
High Voltage Capacitor If the microwave doesn't heat the high voltage capacitor might be defective. The high voltage capacitor works with the high voltage diode to convert the output of the transformer to DC voltage and to double the output voltage. If the capacitor is burned out the entire high voltage circuit stops working properly. The high voltage capacitor can be checked with a special VOM meter which has a capacitance testing capability. Be aware that the high voltage capacitor can retain a charge of more than 3,000 volts and can injure or kill a person if not handled properly. Only trained technicians should perform this type of testing.

High Voltage Transformer If the microwave does not heat, the high voltage transformer might be burned out. Microwave ovens produce a very high voltage in order to power the magnetron antenna, which emits the energy that cooks the food.

Thermal Fuse If the microwave doesn't heat the thermal fuse may have blown. It can be tested for continuity. Watch our fuse testing video for more information.

Thermoprotector If the microwave doesn't heat the thermoprotector may have tripped. This is a safety device to prevent the microwave from overheating. It can be tested for continuity to see if it's blown.

Main Control Board If the microwave doesn't heat the main control board may be defective. This is not common. When a microwave doesn't heat the problem is usually within the high voltage circuit; either the high voltage capacitor, diode, transformer or magnetron.
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Maytag microwave problem everything seemingly works but does not heat. Help

see this causes and fix it. God bless you
Diode The high voltage diode converts the A/C power output of the transformer to D/C, doubling the voltage to nearly 5,000 volts. This high voltage powers the magnetron which emits the energy that cooks the food. If the diode burns out, a lower A/C voltage reaches the magnetron, which is not sufficient to power the magnetron. When the diode fails it is often visibly burned out. If it appears to be good, it can be tested with a volt-Ohm meter capable of testing diodes. High voltage diodes frequently fail and are one of the most common points of failure in a microwave oven.

Door Switch If the microwave does not heat, one of the door switches might be defective. Microwave ovens normally have three door switches, if any of them fail the microwave does not turn on and does not heat. Check the switches for continuity with an Ohm meter.

Magnetron If the microwave oven doesn't heat the magnetron tube might have burned out. The magnetron uses high voltage, high current DC power to generate the microwave frequency that cooks the food. If the microwave oven is turned on when it is empty this can cause the magnetron to burn out. Once it is burned out it has to be replaced, it's not repairable.

High Voltage Capacitor If the microwave doesn't heat the high voltage capacitor might be defective. The high voltage capacitor works with the high voltage diode to convert the output of the transformer to DC voltage and to double the output voltage. If the capacitor is burned out the entire high voltage circuit stops working properly. The high voltage capacitor can be checked with a special VOM meter which has a capacitance testing capability. Be aware that the high voltage capacitor can retain a charge of more than 3,000 volts and can injure or kill a person if not handled properly. Only trained technicians should perform this type of testing.

High Voltage Transformer If the microwave does not heat, the high voltage transformer might be burned out. Microwave ovens produce a very high voltage in order to power the magnetron antenna, which emits the energy that cooks the food.

Thermal Fuse If the microwave doesn't heat the thermal fuse may have blown. It can be tested for continuity. Watch our fuse testing video for more information.
Thermoprotector If the microwave doesn't heat the thermoprotector may have tripped. This is a safety device to prevent the microwave from overheating. It can be tested for continuity to see if it's blown.

Main Control Board If the microwave doesn't heat the main control board may be defective. This is not common. When a microwave doesn't heat the problem is usually within the high voltage circuit; either the high voltage capacitor, diode, transformer or magnetron.


10_1_2012_10_10_06_pm.gif10_1_2012_10_10_34_pm.jpg
1helpful
1answer

Heating problem

see this causes and fix it. God bless you
If the microwave doesn't heat the thermal fuse may have blown. It can be tested for continuity. Watch our fuse testing video for more information.
If the microwave does not heat, the high voltage transformer might be burned out. Microwave ovens produce a very high voltage in order to power the magnetron antenna, which emits the energy that cooks the food.
If the microwave doesn't heat the high voltage capacitor might be defective. The high voltage capacitor works with the high voltage diode to convert the output of the transformer to DC voltage and to double the output voltage. If the capacitor is burned out the entire high voltage circuit stops working properly. The high voltage capacitor can be checked with a special VOM meter which has a capacitance testing capability. Be aware that the high voltage capacitor can retain a charge of more than 3,000 volts and can injure or kill a person if not handled properly. Only trained technicians should perform this type of testing.
If the microwave oven doesn't heat the magnetron tube might have burned out. The magnetron uses high voltage, high current DC power to generate the microwave frequency that cooks the food. If the microwave oven is turned on when it is empty this can cause the magnetron to burn out. Once it is burned out it has to be replaced, it's not repairable.
If the microwave does not heat, one of the door switches might be defective. Microwave ovens normally have three door switches, if any of them fail the microwave does not turn on and does not heat. Check the switches for continuity with an Ohm meter.
The high voltage diode converts the A/C power output of the transformer to D/C, doubling the voltage to nearly 5,000 volts. This high voltage powers the magnetron which emits the energy that cooks the food. If the diode burns out, a lower A/C voltage reaches the magnetron, which is not sufficient to power the magnetron. When the diode fails it is often visibly burned out. If it appears to be good, it can be tested with a volt-Ohm meter capable of testing diodes. High voltage diodes frequently fail and are one of the most common points of failure in a microwave oven.
9_27_2012_10_25_24_pm.gif9_27_2012_10_25_53_pm.jpg
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1answer

Microwave wont heat up food

If your microwave runs, but doesn'theat your food, verify that you have selected a cooking setting. You mayaccidentally set the timer. Test the magnetron by placing 1 cup of water in themicrowave and heating the water for three minutes. If the water doesn't heat,your magnetron is dead.
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1answer

Oven is not making etables heat

If your microwave runs, but doesn'theat your food, verify that you have selected a cooking setting. You mayaccidentally set the timer. Test the magnetron by placing 1 cup of water in themicrowave and heating the water for three minutes. If the water doesn't heat,your magnetron is dead.
1helpful
1answer

Not heating

Hello


Power Supply

Check whether there is a proper power supply. Look to see whether the cord is connected to a grounded 3-prong outlet and the cord is fully plugged in. If the electrical system is built-in and no power cord is visible, replace or reset the household fuse or circuit breaker.

Microwave Functions

Some basic microwave operational steps may affect whether the microwave is heating. Open and close the microwave door, as the unit will not function with the door open, and push "Stop/Clear" to cancel any previous settings, such as the timer, which do not heat the microwave oven.

Setting the Microwave

Once the power to the microwave has been reset, or verified as working, and the microwave is ready to run, select a new cook cycle and press "Start" to see if the microwave begins to run and cook food as expected. Allow the food to cook for the alloted time and then open the microwave door and check to see if the food has cooked or heated. Choose a longer cooking time and restart the microwave if food is heating but is cooking slowly.

Repair

If all efforts to troubleshoot the function and power to the microwave still do not get the appliance heating food as expected, there may be a repair issue that needs to be addressed. Contact professional technician for advice.
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1answer

My microwave comes on lights work but doesn't heat food

The most likely cause is a defective magnetron, "heats food" cost to repair will be close to a new microwave oven.
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Microwave runs but food does not heat

If everything appears to work as normal but does not heat, then the magnetron will be faulty. This is the device which cooks the food, however this can be an expensive part to replace & may not be economical to fix.
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