No Heat My Microwave will not heat I have cheched the magnetron it is not grounded or shorted I have checked the capacitor it is 1.05 mfd. the diode also checks ok the transformer draws around 8 amps on the primary side . it makes a difrent noisy when it runs I dont have any meters to measure the secondary side of the transformer thanks for any help

There are three causes that come to mind, magnetron, high voltage capacitor, and high voltage diode. The diode runs off one lead to the capacitor and the other to chassis ground, sometimes cracks or shorts, the capacitor "silver and rectangular" usually shorts, the magnetron will open in most cases. Unplug microwave, short out capacitor with a screwdriver to remove residual voltage, test with a digital meter, set to ohms and unhook one side of part before test in each case.

Hello,

Investigate these three areas if your microwave won't heat

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's 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.

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.

Hello,

Investigate these three areas if your microwave won't heat

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's 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.

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.

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

Hello,

Investigate these three areas if your microwave won't heat food

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

Hi and welcome to FixYa, I am Kelly

When everything but the heat works there are 2 common components that fail. The high voltge capacitor or the high voltage diode. In rare cases the magnetron fails because the oscillator in the top of the magnetron sticks. When the oscillator sticks the magnetron makes a LOUD humming sound and you do not get heat. However.... a open diode or shorted capacitor will make the exact same sound briefly before the main in line / internal fuse fails.

The capacitor and diode are items 4 and 9 this link:
http://www.appliancepartspros.com/partsearch/model.aspx?model_id=504310&diagram_id=28243249#d28243249

NOTE: Before doing ANY maintenence you must hold an plastic handle screwdriver back on the handle and ground the capacitor terminals at least 3 times. (Just in case it has not failed.)
Failure to do so will ruin your day and pass along one heck of a shock.

To check the diode you must disconnect one terminal first. The read it with a meter. Reverse the leads and check continuity again. It should read continuity in ONE direction / polarity only. Id should NOT read open both ways or shorted both ways.

To check the capacitor you have to remove all the terminals from ONE side of the capacitor terminals. With the meter on R X 10,000 probe the 2 terminals. You should see a brief jump in resistaqnce and then the meter drifts to infinty. Reverse the leads and do this again. You must get the same jump in resistance and then the meter drifts to infinity. If it does not do this it has failed and must be replaced.

If both the diode and the capacitor pass the checks above the next step is to check the magnetron for continuity across the 2 terminals. It must read continuity. Even if this test passes the oscillator can be stuck and it will not heat. (Again if it is stuck it will make a LOUD humming noise.) It is not repairable.

I suspect you either have a bad diode (most probable cause) or bad capacitor (2nd most probable cause).

Thanks for choosing FixYa,
Kelly

Hello,

Investigate these three areas if your microwave won't heat and you hear a loud humming noise/sound.

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 and you will hear a buzzing noise. 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 but you are hearing a buzzing or humming noise. 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, but you can hear a buzzing noise. 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's 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.

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.

Hello,

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

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 and you will hear a buzzing noise. 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 but you are hearing a buzzing or humming noise. 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, but you can hear a buzzing noise. 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's 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.

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.

Good luck.

Hi,

Investigate these three areas if your microwave won't heat;

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 and you will hear a buzzing noise. 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 but you are hearing a buzzing or humming noise. 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, but you can hear a buzzing noise. 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's 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.

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.

Good luck.

Hi,

Investigate these three areas if your microwave won't heat

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 and you will hear a buzzing noise. 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 but you are hearing a buzzing or humming noise. 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, but you can hear a buzzing noise. 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's 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.

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.