My apartment comes with a wall-mounted microwave (KitchenAid KHMC1857WSS) that I clean periodically. While doing so, I see this component mounted on the right-side inside the microwave. It clearly has a dark discoloration, looking like it was burnt or blown out. The component reminds me of sandpaper because it appears to have a gritty surface.
I'm not sure what this piece is, but since it looks burnt and cracked am wondering if it needs to be replaced. Looking at the online user manual it's still unclear what this piece is. For instance, on page 6 of the above PDF, the section titled Replacement Parts, Accessories and Cleaning Supplies does not list any part name that pops out to me as being this piece.
What is this piece inside my microwave?
Best Answer
That's the waveguide cover. It's non-conductive, typically made of a mica/resin-based material.
Yours should be replaced. When you get that degree of carbonization (which should never happen, but eventually does, usually because food particles weren't cleaned off it promptly and left to attract electrical arcs on subsequent uses of the microwave), arcing becomes a lot more likely.
The arcing will eventually destroy the magnetron and possibly other components.
Fortunately, replacement waveguide covers are readily available. It can be a little tricky to get the old one out and put the new one in, depending on the microwave, but not at all beyond the usual household DIY-er. Yours appears to have a simple shape and be secured with screws, which should make replacement very simple.
You can either get a waveguide cover made explicitly for your make/model of microwave, or purchase a pack of sheets that can be used to cut one that fits your microwave. The former is more convenient, but of course costs somewhat more.