Ge jes1358wk02 microwave... controls seem to operate correctly....fan runs... capacitor check ok as does magnetron... but no heat... possibly a little on some cycles... suspect problem is with hi-voltage retifier/diode..but cannot check it with my small volt ohm meter... any other suggestions... from internal noise, it seems that high heat comes on momentarily but shuts down while fan continues to run.. ??

There are three microswitches
When checking a microwave oven that seems to operate properly yet does not heat first check for 110VAC at the primary of the large transformer.

THere are three possibilities, open magnetron "heats food" cracked high voltage diode, or a shorted high voltage capacitor.

Make sure that the program controller is working if not check power - step down supply, the pads are responding- if not faulty pads- or the door switches, if the switch contact are not good then it will not trigger the processor to switch on the waveguides.Since in this case the power level cannot be changed it seems the pads are faulty or the processor has hung up. If so the controller board is a suspect.

If the lights or fan work without any display or action of program being triggered to start then it can be a possible fault on the main board or the processor. Sometimes insect secretion can short the board and display panel and so the processor can work in such an erratic manner. If so clean,solder and reset the board.Now identify the parts by clicking this link: http://www.espares.co.uk/advice/microwave/a/5/141/identifying-microwave-parts.html

If there is no heating please do not switch on unless you have confirmed the fault. It is possible that the Magnetron is faulty, the temperature cut off is faulty or the main capacitor is short. It is also quite possible that insect can get into the oven and create soft spots. When you switch on these will create a short and make the voltage jump and in the long run damage the magnetron.
So Remove cover after disconnecting , check for dirt/moisture in the cabin, if so wipe clean and dry, check the magnetron and area clean and use an jet air to clean off. Check the wave guide covers, if food had deposited
then it must be checked or replaced.

See link: http://www.espares.co.uk/advice/microwave/a/5/1146/how-to-replace-a-microwave-guide-cover.html

Now keeping clear of the microwave, switch on, use a cup of water inside to test.
If you notice any sparks shut off as the magnetron or the main HT capacitor can be faulty. replace with same type.
If there is heating without any issues, you can use the microwave safely

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If there is no heating please do not switch on unless you have confirmed the fault. It is possible that the Magnetron is faulty, the temperature cut off is faulty or the main capacitor is short. It is also quite possible that insect can get into the oven and create soft spots. When you switch on these will create a short and make the voltage jump and in the long run damage the magnetron.
So Remove cover after disconnecting , check for dirt/moisture in the cabin, if so wipe clean and dry, check the magnetron and area clean and use an jet air to clean off.

Now keeping clear of the microwave, switch on, use a cup of water inside to test.
If you notice any sparks shut off as the magnetron or the main HT capacitor can be faulty. replace with same type.
If there is heating without any issues, you can use the microwave safely

Does it make any noises that it didn't before it failed?? It could be a bad secondary interlock switch, cook relay on the PCB, HV circuit problem or bad magnetron. You need an ohm meter to troubleshoot. If you take the cover off, you MUST short across the High Voltage Capacitor terminals to discharge any possible residual charge to prevent shock hazard.

Check the following before you replace the Magnetron device.

1. Check the diode located inside the unit on the noise filter board assembly. it may be damaged.
2. Check the Magnetron Cut-Off Fuse. this will shut off the heating device if there is a fan issue.
3. Check the H.V. Capacitor for burn marks and, discolored terminal points. this will be a sign of a malfunctioning Capacitor device. replace if needed.

If all is ok with the above check list, replace the Magnetron tube.

If there is no noise at all, this suggests that the power transformer isn`t receiving power from the timer/control panel. If you do hear a little buzz when you operate the microwave, The timer/control panel is operating, However It could be a few things which if you are confident enough to tackle, could be sorted by you but bear in mind that microwave ovens can store a lethal amount of voltage which can kill, about 2000 volts for a year or so. Possible causes of your fault are the Magnetron, Power transformer, Capacitor, Diode or even the control panel that provides power for the power transformer if you don`t hear the buzz. Have you got a meter?? Yes? Switch it to X10 ohms. Next, Unplug from the power socket and remove the casing, discharge the high voltage capacitor with a pair of well insulated snipe nosed pliers covered in a thick dry towel. Next, place the meter leads between the capacitor where the thick lead enters, and the casing of the oven. Does the meter read anything? No? You need to find out if the transformer is receiving power from the timer/control panel. If it is, the Magnetron will be US or the heater supply is missing to the magnetron. If the meter reads, The diode/capacitor or magnetron is short circuit. Disconnect the thick leads which are connected to the capacitor, Check for leakage across the capacitor again, Yes? Magnetron OK. Some diodes are built into the capacitor. On models where the diode is visible, (A black device going from the capacitor to a screw holding it to the casing), either unscrew the screw or disconnect the connector on the capacitor, now read the capacitor connector, if OK, no reading, Diode US, If there is a reading, the capacitor is US. If there`s still no reading, read the lead which you removed from the capacitor which goes to the Magnetron, If it reads, the Magnetron is Short Circuit. To check the heater, connect your meter across the two connectors on the magnetron, If it reads, the heaters are OK, read across the two wires that you revoved from the magnetron, if it reads, the Transformer is OK, if not, a new Transformer is reqiured. If not, they are O/C, New magnetron required. I hope this helps, Ian

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.

If it is working but not heating, then test the high voltage capacitor,the rectifier diode.or the magnetron. If all this are fine, test the control board.

The diodeand capacitors can be tested. The capacitor must be allowed discharge before testing, or you risk to get electrocuted, evenif power is off.Capacitors can get discharged by shorting their two contacts.
Before replacing the magnetron test also the control board.
Replace the magnetron if the checks and all of the high voltage component tests are good, but the unit still does not heat.



All locations, and description of this parts can be located using the diagram here: Counter top.

Parts must be tested to find out what is wrong.

Remember that microwaves are potentially dangerous devices if not repaired properly, the job must be done by a competent person.
A microwave energy leakage test must always be performed when the oven is serviced for any reason.

Regarding parts, contact the seller here to purchase parts.

You can also order from MicrowaveSvc , they also provide parts.

hi possible magnetron problem but also check highvoltage capacitor and diode . the process of ellumination is the only way to help u .first disconnect connegtor to magnetron and switch oven on if noise goes away eureka repeat with other components