I know this is an old thread but I found it when I had the same thing happen on my Dyson Multi Floor 2. Brush bar would come on and off intermittently. My solution ended up being a little differant so I wantes to share in case anyone else came across it. When you remove the brush head, there is a grey clip and the whole thing slides off. Part of that is a plug assembly on top. On my machine the female side of the plug that stays with the main machine, the contacts inside had come loose in their holder. There is a clip of sorts that holds them in and it had come unlatched. All I had to do was remove one screw on either side of the plug to slide the cover back and gain access, pull the plug out a bit, push back in and turn the contacts so they were fully seated and rotated so the clip's ears held them forward, press the clip back down with a pair of pliers and reassemble. My wife tested it out and it seems to be working perfect now. Wish I had tried it before spending $300 on a new Shark Cordless, ???