[rverdlm]

The fan motor is mounted through 4 rubber gromets. My guess (happened to me) is that one or more of these gromets is bad. You should also check both squirel cages because just a little dirt will make them out of balance and that is what causes the grommets to go bad. Also don't wait to long to fix it or you will wear the hole in the metal bracket that holds the grommets and then you will need to replace that also. I went down this road 2 years ago with my bedroom a/c and this fixed it, so far so good!