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Repair and disassembly guides for GE Microwave ovens.

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GE Profile Microwave is blowing through door switches

I have a Profile microwave that’s about 10 years old. A couple of years ago it stopped working, and the problem turned out to be the door switch. (Surprise!) I replaced the switch, and everything was fine for about 6 months. They it stopped working again. Door switch again. Fixed. Good for about 6 months. Dead switch again. What’s going on?

I see two likely causes. 1) I’m buying $5 switches off Amazon instead of the $40 OEM switches from Sears Parts Direct. 2) There’s an issue with the microwave that’s causing it to melt switches. And melted they are. The bottom lead is consistently melting the plastic that supports it, leaving it twisted at a 45 degree angle. And it’s always the same switch.

Occam’s Razor says it’s that the switches are cheap, but before I go spend $40 for a tiny, unispired bit of plastic and metal, I thought it was worth asking the question. Anyone have experience with cheap switches dying or microwaves killing their switches repeatedly?

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I am also experiencing a similar issue. The top door switch starts to fail. At first the turntable and cooling fan continue to run if the door is open. (They are normally off with the door open) Then shortly thereafter, when attempting to cook, the magnitron will not work but the timer counts down like normal. The top switch is not melted but it appears that the button return spring has failed and the switch is stuck in the closed position. I'm about to replace this switch for the fifth time.. Good thing I bought a 12 pack from Amazon!. Any thoughts on the root cause of this issue?

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The cheap switch is only part of the problem. Microwave ovens are meant to be shutoff before opening the door. This is not a problem on smaller ovens as the smaller amperage discharge across the switch when you open the door does not harm it. There are two interlock switches one for each leg of the transformer that powers the magnetron, one switch completes the circuit to send power to the relay which then sends power to one leg of the transformer, the other door interlock switch is directly connected to the other leg of the transformer. This is the switch that goes bad when you open the door with the unit on. Transformers work by magnetic charge, when you open the interlock switch the voltage in the transformer will jump the switch eventually destroying it. The relay on the other leg of the transformer can handle the on/off amperage. Go with a better switch. The manufacturer could put in a heavier switch as they use the same switch for small and large ovens but it is unintentional planned obsolescence. The third interlock switch is called the monitor switch and it shorts the power to the transformer blowing the fuse if the other interlock switch gets its contacts locked together or is bypassed.

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Hi @templedf ,

If the plastic is melting then it means that too much current is flowing through the switch and it is getting hot. So the problem is most likely the other component(s) that the switch is connected to. If the switch has the correct power rating then it won’t get hot if the other components are OK, The switch voltage and current ratings should be marked on it

Depending on which switch it is it may be the magnetron circuit, the fan circuit or the motor circuit etc.

You would need to have the schematic of the oven or at least to trace the wires from the switch (one side would most probably come from the input power connection) and check where it goes to and then check the components if the switch is rated correctly.

Be safety aware when working in microwave ovens as they are dangerous if you don’t know what you’re doing.

The HV capacitor can seriously injure you as it can store enough voltage (>6000V DC) for months, even if the oven has been disconnected for this amount of time. It needs to be discharged correctly before attempting any repair work. Most simply short out the terminals on the HV capacitor to dissipate the voltage but this can damage the capacitor or if an inappropriately sized screwdriver was used can actually weld it onto the terminals. Most people doing it this way are too impatient to do it correctly. Make a lead (12 gauge wire) with alligator clips at each end and a 10W 1 MegOhm resistor in series i.e. clip- lead - resistor - lead - clip, and connect it between the +ve terminal of the capacitor and the chassis and let it discharge the capacitor. Wait for about 5 minutes and then use the screwdriver to dissipate any residual charge that may be still there just to make doubly sure.

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I checked the power rating of the OEM switch and the switch I'm buying, and they're the same. After thinking about it, I realized there is one more detail worth pointing out. When the switch failed the first time, I took it apart and sanded down the contacts, and it worked for a couple more months. When it failed the second time, it wasn't melted. It's only these $5 switches that are melting.

For now it's working with another $5 switch in it. When that one blows, I'll do a careful check of where its power is coming from. Thanks for the advice.

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@templedf

It may be that you're getting what you paid for.

With the first switch you said that you had to file down the contacts, presumably because they were pitted. This indicates contact wear over time due to current flow. If the material travelled from one contact to the other contact i.e spike of contact material going into hole on the other contact, then this is contact migration and is usually caused by sparking as the contacts open. This could occur over time if the microwave door was opened often before the cooking was finished to stop the operation and the oven is turned off by the interlock switches operating/releasing instead of by the control board as it should be. The interlocks are a safety device to prevent microwave radiation escaping out of an open door if the oven was operating

It may be that the new switches the material of the contacts is getting too hot (which it shouldn't) and that the insulation has inferior plastic. Again it shouldn't but who knows.

You need to check where the power is going to, from the switch, not where it is coming from, to the switch and check there.

It is coming from the supply but if for example the magnetron has some shorted turns in the windings there is less resistance therefore more current flow through the switch. This may not noticeably affect the magnetron's performance but it will have an impact on the switch

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Try buying the actual OEM part. I would get from a local Appliance parts dealer. In Seattle I use Apex Appliance on Aurora.,

Inspect it at the store and see if it looks materially different? If the wire you say is melting is larger, that could be your issue.

I also wonder if the microwave itself could be cooking the switch? It’s an odd theory, but a switch doesn’t usually have high voltage, its usually just a gate for the rest of the circuit; If SOMEHOW the microwave was leaking radiation onto the switch, that could be an explanation too. wrapping the wire in foil tape might help this. Just crazy thoughts, I know.

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Hi,

As can be seen from this microwave oven example schematic mains supply voltage is connected to the interlock switches. Even 120V AC can be too high if the switch has the wrong rating or if there is a problem further into the circuit.

Cheers.

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HI @Bocellidad

If it is a mechanical problem with the switch (was the switch casing fractured etc at all, jamming the spring?) and not electrical and if all the previous replacement switches were from the same source (manufacturer) I'd be looking at changing to a switch from a different manufacturer.

Search online for (insert make and model of microwave oven) parts to find more appliance orientated suppliers of parts for the oven and check their prices for the switch, e.g repairclinic.com, searspartsdirect.com, partselect.com or appliancepartspros.com

It may be a case of you get what you pay for, if the parts suppliers’ switches cost more than those bought from Amazon.

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Daniel Templeton さん、ありがとうございました!
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