What to do when the brush roll isn't turning
The first step in troubleshooting a Dirt Devil vacuum cleaner that isn't spinning its brush roll is to check for debris and tangled hair in the bearings on the side of the brush roll. When hair and other debris become entangled in these vacuum parts, the power brush motor often overloads and trips. After removal, push the reset button, and then check to see if that fixes the issue. If the brush roll still won't turn, a worn belt or bad drive motor could be preventing the brush roll from turning.
How to replace the brush roll in Dirt Devil upright vacuum
Unplug the vacuum to disconnect electrical power then remove the bottom plate. Pull the brush roll out slightly and release the drive belt from the brush roll. Pull the brush roll out and insert the new one in the base. Work the drive belt onto the new brush roll and reassemble the vacuum.