Well Iggy, true to Forest River form,, the microwave installation instructions were almost useless. Your information about the piece of wood in the cupboard, was spot on. It was stapled in the front corners, pried it up and found a piece of 2x8 running the width of the cupboard.
No L brackets, just 6 large 1/4 x 3 inch screws through the wood and into the top of the microwave. They obviously knew what they were doing, all the screws entered into empty areas of the microwave top.
According to the micro wave instructions, to change the charcoal filter you remove the 3 screws holding the vent to oven, they are on the top, pull those and then slide the vent grill to the left. Swing out the top and it easily removes. Only problem is Forest River installs the microwave with those screws under the cupboard.
With that grill removed, you can then drop the control panel off the microwave, but wait, no fuse there. It is further in and there are 2 20 amp 250 volt ceramic fuses on a separate board is just right of the cooking area, at the top, you have to remove a small internal grill to gain access.
Btw this was all done after I removed the microwave from under the cupboard and set it on the table. To make sure we can get at the fuses and the filter in the future it was installed under the cabinet without the 3 screws on the top for the vent grill. Once snapped into place and slid to the right, it locks in very securely.
So the dealer says, "oh wow that will be a pricey fix, when those microwaves stop working it is not good" "Could be upwards of a grand"
2 fuses, cost $5.61 taxes in, about a total of 1 hour of my time and presto, microwave works like a charm. One of the fuses had blown, that's all.
Thanks again for your help, and I hope this info can help someone else.
John & Gail
21 years, 2.6 million miles, accident free. I earned my spot on the road.
2008 Georgetown 350SE TS