GE Microwave making buzzing sound and not shutting off

[CV209]

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Hi all. Need some help diagnosing this issue. My GE Microwave model JVM1440WH04 is having 2 issues.
1st it has been working but making a buzzing sounds while running. It still works but the buzzing has become louder over time.
The 2nd issue is the microwave is making a humming sound with the door closed. No light or fan is on. Just makes a humming sound with the door closed. It stop when I open the door.

As far as I can tell the door issue is most likely a replay. I am unsure if the loud buzzing sound is the magnetron, the diode, or a separate issue. Any input would be appreciated. I can always take a video of the issues if a professional can send me in the right direction. Thanks all.

[Doc Ryan]

It sounds like you might have two separate issues going on.


The loud buzzing while the microwave is running – This could be a failing magnetron, a high-voltage diode, or even a capacitor. If the microwave is still heating properly, the diode or capacitor could be on their way out. If it's not heating well or takes longer to cook, the magnetron might be the culprit.


The constant humming with the door closed – This is likely caused by a stuck relay on the control board or a faulty door switch. Since the microwave isn’t turning on but still making noise, something is partially energizing the circuit.


Important Safety Warning:
Microwaves contain high-voltage capacitors that can hold a dangerous charge even when unplugged. Do not attempt to test or replace high-voltage components unless you are experienced with microwave repairs and know how to safely discharge the capacitor. Accidental contact with high voltage can cause serious injury or electrocution.

Part Testing

• Check the door switches for continuity with a multimeter. If any fail, they need to be replaced.
• Inspect the high-voltage components (diode, capacitor, and magnetron). The diode can be tested with a multimeter set to diode mode, and the capacitor should be discharged safely before testing.
• This video shows how to test a capacitor.

[CV209]

So I took the microwave apart and did some digging. The door issue is a faulty relay. I tapped it a couple times and it works for now. I ordered a replacement. The 1nd “buzzing” issue persists. The microwave turns on as normal, starts heating, then after about 5 seconds the buzzing kicks in. Doesn’t seem to affect anything for now but something is definitely going out.

[Doc Ryan]

It sounds like you nailed down the door issue, nice job on identifying the faulty relay! That should be a solid fix once the replacement arrives.


As for the buzzing that starts after 5 seconds, that’s a strong indicator that something in the high-voltage system is starting to fail under load. The fact that the microwave is still heating suggests the magnetron is likely the culprit, but it could also be the high-voltage diode or capacitor struggling when current builds up. Keep me updated on what you find!