Yeah...Macie was terrified of the vacuum when we got her. (Along with lawnmowers, hula hoops, her reflection, and water....haha!) She would not come out of hiding if she caught a glimpse of a vacuum cleaner. I guess this won't help you out much now, but honestly, she just got used to it. After a few weeks, Macie would just bark at it and chase it, and eventually she realized it was no threat to her. Maybe just by keeping it at a safe distance for now Chopper will learn it's okay. Okay...that might not have helped at all. Hope it works out!