First time we used the microwave tonight we heard a clanking sound from the fan. If you have a Sharp Carousel Convection Microwave Oven Model R-1874-T (or possibly similar) and the same issue, here's how I easily resolved it. It appears that my unit was a bit too aggressively attached to the PC. I set the oven to preheat, so the fan would run, then I removed the removable silver filter from under the microwave (picture one, below) then with a Phillips screwdriver, I backed the silver screw (top left in picture two) out a tiny bit at a time until the clanking stopped. It didn't take but a quarter turn, at most. Awesome convection/microwave, by the way.
-Mike
