Kenmore isn't exactly a brand - Kenmore doesn't manufacture anything - they rebrand other manufacturers appliances. Most MWs are made by Sharp. The rest are made by GE, Panasonic and maybe one or two other manufacturers. Different model Kenmore MWs can be made by different manufacturers.

So when Consumer's Guide recommends the particular Kenmore model number, it can be by any one of those brands under the Kenmore label? But then I'd assume that Kenmore model recommended was one of those... we have had one of the Sharp brand microwaves before & was satisfied with that one.
Odd, that when experimenting with this problem yesterday, a cup of coffee was heated to the regular hot temp but any food on a plate UNDER the plastic shield/cover (used to prevent splashes inside the microwave) would not get hot- just a bit warm! Little by little we played with different things & think (!) that the cover has gotten heated so often & surface now prevents things under it to get hot! Going to get a new cover to see if that makes a difference... will update this later to see if that may be a simple problem!!

Not exactly - a particular Kenmore model will be made by a particular manufacturer but a different model number may be made by a different manufacturer. In the past, people have posted a list that lets you determine who manufactures which items. Typically Sears contracts out to particular manufacturers to build the items for them - they'll be similar to the manufacturer branded items but sometimes with additional features. What's really odd about CR is that sometimes they'll give the Kenmore model a good rating and yet give the comparable item from the manufacturer a bad rating.

Interesting, we went to buy another microwave but decided to try buying a new microwave cover first. Well, THAT was the problem !!: the old cover became too ? opaque or something so the microwaves didn't penetrate or ?? so a $3 new cover fixed the problem!
Hope this might be useful if anyone has this similar problem in the future ... or maybe this is already something we should have known about?!

Never too old to learn something new, huh?!

I do realize that a lot-if not most- of the info. regarding items comes from the yearly questionaires we get from Consumer's Guide as subscribers; this may be the most accurate & informative!

What you report about your plate cover being the problem is in the short-list of most bizarre things I've heard!

The leading three digits (before the period -- xxx.xxxxxxxxxx) in Kenmore model numbers indicates the source manufacturer. Coding lists can be found online, search for "kenmore manufacturing codes" or some such.

Well, bizarre or not... this is what happened! Tossed the old microwave cover (for containing splatter of foods while heating), bought a new one & now food, coffee heats to the usual hot temps. whether under or on top of the new plastic cover ! Seeing is believing here & $3.00 vs. $200 new oven.
Welcome any ideas of why/how this happened!