how do I mend the belt on my Dyson dc04?

Someone had asked your question slightly differently, and I found this answer which might help you.

To replace the belts on the dco4 clutch model
1 remove brush roll
2 remove the control knob,
this can be done by pressing down the hidden locating catches ,one is located adjacent, to and inline with the large dot on the control knob, and the pressing can be achieved by inserting a thin screwdriver blade into the
groove next to the dot,this releases the top catch,the other catch can be located directly opposite on the underside,again insert the screwdriver as detailed above, the knob can be completely removed, and now the clutch can be removed and dismantled with standard engineering tools, great care must
be taken to replace all components in order as they came off this will ease re-assembly, good luck,

jim
February 2005

Jill
June 2005