Microwave seems to come on, but only heats occasionally?
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,
Is this a good question?