Why won't oven heat?

please follow this steps and fix it. God bless you

1. Check the power diode This 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 capacitor Responsible 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 magnetron Responsible for generating waves and producing heat. When your microwave is no longer heating properly, replacement will be required.
   
4. Thermal Cutoffs Examine 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.
   

follow this test and fix it. God bless you

1. Check the power diode This 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 capacitor Responsible 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 magnetron Responsible for generating waves and producing heat. When your microwave is no longer heating properly, replacement will be required.
   
4. Thermal Cutoffs Examine 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.
   

please follow this test 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.
   

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.
   

see this cuases and fix it. God bless you
Microwave Runs, but no Heat OK, get ready, this micrwave oven repair can take some time. This is where you must be able to read a wiring diagram and do some "live" checks on parts. First easy check is to make sure power is coming off your control board at the MW relay. Make sure of the wires and test here, if you have 120 volts at this point, you have ruled out a lot of parts that could be the problem. You have now ruled out any switch problems, control board problems, or a thermostat or 2.
If you do not have power from that MW relay on the control board, you must trace the wiring back to see if the proper voltage is going through your switches, any thermostats, and arriving at your control board. Your wiring diagram on your sheet will show you where and what to test. Below is a general switch test troubleshooting guide.

If the proper voltage is coming into your control board and you are not getting voltage at the MW relay, then you need to replace the control board. If voltage is interupted by a thermostat or switch from your testing to the control board, then replace that part.Now, testing from the MW relay on to your transformer, high voltage capacitor, magnetron, and diode. Do not do any voltage reading from the secondary side of the transformer on, this can be a deadly microwave oven repair if you do not follow directions. This can result in electrocution and the "blowing-up" of your voltmeter, only do OHM testing with the power off and the capacitor discharged. Someplace in this circuit, usually before the transformer, you will have another thermostat to test. It is usually mounted on the magnetron. Do a quick OHM test to see if it is open or closed.
Now to test either the transformer, high voltage capicitor, magnetron, and diode, you must test each part separately. A good rule of thumb, if your capacitor is bad, change the diode also. Another note, if you are working on an OTR model and you have determined to be one of these "heating" circuit parts, you can not test these parts until you take the unit down. If you don't have the parts with you and you have to order them, order the magnetron, capacitor and diode and you will have a 90% chance of solving the problem. If it is an older microwave, order the thermostat also, most times you can return un-used, un-opened parts. Check with your parts supplier. This way you only have to take the unit down once.
To test these parts, scroll down this page and you will see a chart with component tests. Follow the instructions to find which part(s) are defective in your microwave oven repair.

There are a number of possible causes for this. Most of the troubleshooting requires a multimeter. However, first you should check whether the oven is actually not heating, or whether there is a problem with microwave distribution in the oven. In a large microwave safe cake pan or pie plate, put just enough water to cover the bottom. Put it in the oven and turn the oven on high. If you see one spot where the water boils away quickly, you have a non-functional microwave stirring fan. Food will not cook unless it is in this hot spot. To fix it, take off the top cover, and look for the big fan in the waveguide duct coming from the magnetron on the right side (not to be confused with the small magnetron cooling fan blowing air across the magnetron's fins). If memory serves me correctly, you have to remove a cover plate on top of the oven cavity, and the fan is belt driven by a small shaded pole motor near the back of the oven. Make sure the fan spins freely. Clean and lubricate the bearings with a light-weight oil if necessary. If the fan turns freely, make sure its motor has power when the oven is supposed to run. If all is fixed, the wet plate test should show more even heating, and food will cook properly.

The other possibilities, together with diagnostic procedures, are listed below.

• Backup door switch*: With the oven unplugged and the door closed, remove the top/side cover. There is a large transformer on the floor of the oven on the tight side. The primary terminals are towards the front. One terminal on the transformer is connected to neutral (white wire). The other goes to the backup door switch, and the other terminal on the door switch is connected to the controller relay (sometimes there is also a thermal cutout in this line, but that part is usually in the incoming power hot lead). Measure the resistance from the relay terminal connected to the door switch to the hot wire on the transformer. It should be much less than 0.8 Ohms with the door closed. If not, check directly at the door switch, and check any other devices wired between the relay and transformer.
• High voltage capacitor. This is an oval cylinder behind the transformer, on the high voltage side. It is about 3-4" long, 1" in the narrow dimension, and about 2-2 1/2" in the longer oval dimension. It has one lead to the transformer on one terminal, and a lead to a diode and another to the magnetron on the other terminal. Make sure it is safely discharged before testing. Measure its capacitance and compare it with the value printed on the side. If the capacitor is open, the magnetron won't work. If it is shorted, usually the fuse blows. Caution: when you reconnect the capacitor, do not interchange the two terminals. The capacitor is polarized, and applying a reverse voltage may cause it to explode.
  
• Relay. This requires a live test, with great care. Stay away from the backside of the transformer - 1200-2500 Volts is not a good thing to mess with. Measure the voltage at the transformer's hot terminal on the front (primary) side with the oven running (the other voltmeter lead can go to either neutral or ground; you are more interested in presence or absence than in accuracy). If you get nothing, check the relay terminal on the controller (make sure you are looking at the magnetron terminal, not the lamp/fan terminal). If you get nothing here, the relay is bad or has a bad connection to it.
• Magnetron or diode. If you have voltage on the transformer primary, but you get no heating power, the only items left are the magnetron and diode (assuming the capacitor passed its test). The only safe way to determine which, other than substituting parts, is to measure the DC voltage using a special high voltage probe on the capacitor's diode/magnetron terminal. If you have 0 Volts DC, or a DC voltage much less than 1000 volts, the diode is bad. If you have the full voltage, the magnetron is bad (only thing left). Warning: do not try to measure this voltage directly with an ordinary meter. It will destroy the meter and could be very dangerous for the operator. Use either a high voltage meter or a high voltage probe made for use with digital multimeters.

* The main door switch is not the problem. If it is open, the oven will not run. Its job is to turn off the fans and magnetron power relay if the door is opened while the oven is running. The backup switch is a second disconnecting means in case the relay is shorted.

9 times out of 10 this is usually this is a bad magnetron, the other time is sometimes a bad high voltage diode. See components section. Many thing can do this but, common things are....loose high voltage wire.....poor solder joint on board.....magnetron.....power relay..... Q - The microwave display counts down and the inside light is on, but nothing is heating and the fan is not running.
A - This most commonly is a bad door switch, other possible problems are a faulty relay or solder joint on the power module, but a bad door switch is most common.

Q - The microwave makes a loud "hum or buzz" noise but will not heat up the food?
A - 9 times out of 10 this is usually this is a bad magnetron, the other time is sometimes a bad high voltage diode. See components section.
Q - My microwave is running and sounds like it is working but will not heat up anything.
A - Many thing can do this but, common things are....loose high voltage wire.....poor solder joint on board.....magnetron.....power relay.....
 Q - The microwave display counts down and the inside light is on,  but nothing is heating and the fan is not running.
A - This most commonly is a bad door switch, other possible problems are a faulty relay or solder joint on the power module, but a bad door switch is most common.
Q - The fan in my microwave oven is not running will this hurt my microwave?
A - YES, the fan cools the magnetron and electronics, take the microwave in for service, most fans are not too expensive to replace.
Q - My microwave blows the fuse inside itself as soon as I push the start button.
A - Usually a shorted high voltage capacitor...see components section.

Q - The microwave makes a loud "hum or buzz" noise but will not heat up the food?
A - 9 times out of 10 this is usually this is a bad magnetron, the other time is sometimes a bad high voltage diode. See components section.

Q - My microwave is running and sounds like it is working but will not heat up anything.
A - Many thing can do this but, common things are....loose high voltage wire.....poor solder joint on board.....magnetron.....power relay.....
 Q - The microwave display counts down and the inside light is on,  but nothing is heating and the fan is not running.
A - This most commonly is a bad door switch, other possible problems are a faulty relay or solder joint on the power module, but a bad door switch is most common.

Q - The fan in my microwave oven is not running will this hurt my microwave?
A - YES, the fan cools the magnetron and electronics, take the microwave in for service, most fans are not too expensive to replace.
 

PLease open the housing of turn table motor at bottom of the oven and check for the AC input voltages on motor terminals as specified on sticker on motor. for no heating please check fuse between high voltage transformer and high voltage capacitor. Also check high voltage Diode and Magnetron.Please please don't try to measure voltage on terminals of magnetron.