Chosen Solution
I have a Kitchenaid Microwave KEMS378GSS0. So the lights on, the fan’s running, and the carousel is turning, but only intermittent heating. Before you jump in with the magnetron needs replacing, please read on. The thing is, I’ve found pushing on the door handle or a light ’thump’, is usually enough to start the microwave heating when it’s not (or stop it sometimes, if it was heating.) There’s a noticeable ’thrum’ (noise of some electrical part engaging) when that happens, even after the microwave has already started. I figure it’s either a bad sensor or a mechanical issue like a loose connection or bad switch… but I was hoping to narrow it down before pulling out and apart our 8 year old built-in combination microwave & oven. I do have some (slight) experience with repair work and circuits, but the expanded parts diagram really doesn’t help show how everything is connected. At the moment the best I can come up with is one of the three microswitches that are part of the latching assembly serves as an additional safety keeping the magnetron from engaging and it’s going bad?? That’s where I’m stuck. It’s the best I can guess at, but it doesn’t make sense to me why the microwave would come on at all instead of just reporting a door open error if one of the switches was intermittently working. So I’m here looking for experience with microwaves… Someone familiar with their design and/or repair who might make other suggestions as to what to look for when I do try and fix this beast. Or maybe someone that can confirm if it makes sense that one of the latch microswitches going bad (sticking, whatever) could in fact allow the microwave to come on but not heat up. Thanks for reading, Dan
For anyone interested, I did finally fix this. Replaced 3 door switches to no avail. Further checking while it was apart revealed that the door wasn’t closing 100%, so one of the door switches (interlock #2) wasn’t engaging. Top part of door looked spread slightly, which seemed to be what was keeping it from working. Maybe a result of taking the door apart repeatedly to replace the torsion springs. I finally just dremeled the inner edge of the two latches on the door so that the rotating mechanisms that the microswitches sit in could turn an extra mm further. (a little counter-intuitive because the latches first turn the disks inward, but when mostly in the springs push the disks in the other direction so that the latches are then keeping the disks from turning further.) That pretty much did the trick. Not perfect, but the switches do engage 95% of the time when closed. If not and the light’s on, a light push or tap is enough for it to register as closed. PS. As I was trying to fix this, the MW changed to beeping error that the door was open, where before it would actually turn on but magnetron wouldn’t engage. With a little searching I found the Buss fuse had also likely failed, probably as a result of my tinkering. Another trip to hardware store for a $3.50 part and it’s back to working!
Most of us won’t work on these because they can kill you. The consensus seems to be to chunk it and get a new one. FYI - Here’s how to discharge one: https://www.youtube.com/watch?v=VzQm59tV…
It must be frustrating when you have to answer your own question. My microwave, after working for 10 years, suddenly seems weak. It takes 4 minutes to get 1/2 cup water from cool to lukewarm! All i want to know is if the fact that it still sort of heats (barely) means that the diode and magnetron are ok and the problem is elsewhere?
