To make a very long story short, I dropped a piece of Styrofoam down a vent duct in our master bed. It dropped three stories to the basement, straight down. I was trying to fix an expansion/contraction problem and it accidentally slipped out of my hand.
Now when the AC comes on/off, it shakes, rattles and rolls. . . all the time. Tough to sleep at night. I tried fishing it out with a shop vac and a pool filter hose but that didn’t work. (My kids thought it was neat that I was built the world’s longest vacuum cleaner)
Of course, it is a finished basement and all of the duct work is covered by drywall.
This forums has always been incredibly helpful to my DIY efforts. So before I take a sledge to the drywall . . .