#Solved
Our microwave has just begun to show a failure mode. With no settings on the timer/modes when we close the door we hear a 60-cycle hum.
We put a coffee cup with water in and closed the door but did not push any button and noted the hum. The water got warm, for the exposure of 20 to 30 seconds, the water got the expected level of warmth we think.
Is there any danger if we leave the door open? (No hum with the door open)
Could the Magnatron be running at a higher output than it is supposed to when the door is closed but the microwave is not under the control of its built-in circuitry?
Of course, there is no danger of the microwave doing anything other than heating stuff (No mad science going on)? We know that microwave ovens work by making the water molecules vibrate faster.
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When microwaves were new technology, it was fairly common practice to just never leave it empty. My grandmother always kept a large glass of water in it, even when she wasn’t using it.
My only thought is that it was a safety thing that they were taught which has fallen off because the tech got better.
For the time being, if you DON’T want to unplug it (I think you should) maybe that’s an option? Just always ensure it’s got a glass of water in it.
What’s the reasoning behind keeping a glass of water in it? I’ve never heard of that before.
To give something non-flammable that can absorb the energy, instead of starting a fire. The reasoning being that if you mysteriously see the water boiling, you can unplug the microwave before it starts a fire.
I thought it might be something like that. When microwave ovens were a new idea people had some odd misunderstandings regarding safety.
The unit is now unplugged and we will be replacing it soon. We have gotten good use out of this one and it has earned its rest. (LOL) I will keep an eye out for the feature you mentioned “Inverter Technology” thanks for the heads up.
I had tried the power cycle because the timer part of the microwave is a small computer, perhaps a reset would bring it back to normal operation. No, it did not. It seems perhaps the relay that the timer opens and closes to energize the magnetron is probably stuck closed.
I’m not an expert but I believe microwaves are generally designed so they can’t run with the door open unless you very intentionally modify them to do so. They shouldn’t fail in a way where it’s possible. That may not be correct, and I would say that regardless you should replace a malfunction microwave because it’s inherently unsafe for other reasons too.
We intend to replace it soon. In the meantime, we will leave the door open. We do not hear the humming sound when the door is open. Do you suppose we should unplug the unit? (nontrivial as the unit is an over-the-stove kind with the plug high in a cabinet above the microwave and of course, in the back of the cabinet.)
I would definitely unplug it. If you, someone else, or perhaps even a pet accidentally closes the door and it turns on with nobody realizing it bad things can happen. It will basically microwave itself and if you leave it running long enough it creates a big fire risk. It is a small mistake to make with a high risk.
It has been unplugged. I did try unpluging - wait - repluging (reconfiguring the primary power coupling) but that did not resolve the issue.
Ya, it couldn’t hurt to unplug it. Once an appliance starts malfunctioning I’m always concerned about it starting itself on fire. I don’t think it’s especially likely but it feels like it’s worthwhile to mitigate the potential.
The biggest risks with a dying microwave aren’t you being blasted by microwaves (although this can happen). It’s fire because the magnetron coils heated up and melted their insulation and shorted out.
If a fire occurs INSIDE the microwave DO NOT OPEN THE MICROWAVE! Leave it closed and unplug it or pop your circuit breaker.
Smaller fires will typically burn out inside a microwave due to lack of fresh air.Once it’s unplugged, you can use a Class ABC (or Class K) fire extinguisher and then open the door and blast it IF it seems like the fire might not be dying down or is growing. This can be pretty dangerous as a giant plume of fire and smoke will shoot out if you open the door and can cause the fire to spread rapidly so use your best judgement.
For fires in an oven, just leave the door closed. It will burn out due to lack of oxygen. Have a fire extinguisher on the ready though.
When in doubt, leave the area and call for your fire department.
In terms of microwave leakage, this is highly unlikely unless there are obvious holes in the microwave. Modern microwaves have pretty substantial shielding and safety mechanism to prevent microwave leakage.
You’d also know pretty quick if you’re being hit with microwaves. The areas where it hits you would heat up and be pretty uncomfortable.
Another telltale sign of excess microwave leakage is it kicks everyone off 2.4 GHz wifi because it over-powers the signal. This was actually a pretty frustrating problem back in the day when wifi was new and wasn’t able to handle interference as well, lol. You’d know someone was microwaving something because your signal would drop substantially.
The second risk is electrocution. Microwave transformers are no joke and you should never ever take a microwave apart unless you know exactly what you’re doing.
If you’re getting a new microwave, look for one with “inverter technology” as these allow for actual variable power output instead of just altering the duty cycle. In other words, with the “inverter technology” the microwave uses less energy to emit lower energy microwaves. This will ensure your food is always being hit with microwaves and actually heats better and more evenly.
This is contrary to your run-of-the mill boring microwave which uses “duty cycles” which is a fancy way of saying “how long is the thing on emitting full power vs. how long is it not” which will heat up food unevenly.
We went shopping Monday night. We are limited to one store where we have available credit. None of the available units seemed to have “inverter technology”, but the one we got has Convection Oven and what they call “Slimfry” or air fryer features. We are looking forward to the installation later this week, boiling water on the stove for tea is so back-at-the-mouth-of-the-cave.
Of course there is no risk of microwave doing anything other than heating stuff. Based on what you have written it seems like the circuitry that controls the timer is malfunctioning. I have seen it happen to a microwave and we ended up just replacing the timer.
