I have a Dyson DC77 animal + allergy upright vacuum. I assume the design of my vacuum is similar to the DC24. The DC77 is bigger and has added paper filters behind the "ball" wheels. I had the same problem with mine. A small lever switch inside the vacuum "ball," which controls power to the beater brush, is turned on when you move the handle from the vertical position to any other position, and turns it off when you place the handle back in the vertical position. If you remove the "ball" wheels you should be able to see the switch on one side, and the plastic assembly that turns the switch on and off when you move the vacuum handle upright vs. horizontal. In my case, the beater brush was intermittent. Sometimes it would run and sometimes it wouldn't. Once I disassembled my vacuum far enough to access the switch, I checked the continuity of the switch as I pressed down on the switch. Though it seemed unlikely, I actually found a dead spot on my switch after it turned on, but while pushing the switch lever...