You can tell if your DC04 needs two belts by answering this question: Does your DC04 have the brush control knob that allows you to turn off your brush roller? If yes, then you will need two belts and you might consider replacing the entire clutch. Check out this video: http://www.youtube.com/watch?v=7_CtaFcc5HU It is possible to replace the belts inside the clutch but it may require some practice and a steady hand. If no, you just need one and it is a simple belt change.
www.bobsroswellvacuum.com, October 2008
