I have the same problem. I disassembled the housing for the brush and started the vacuum to see if the motor would run and stay running with the belt disconnected, same result. The motor runs for a few seconds then stops. I replaced the motor, same result. There is a small circuit board that the motor plugs into (they call it a wiring harness). I will replace this board and retry. My thought is that maybe a capacitor or transistor is going bad on this board causing the motor to stop running.