May well be the motor on the way out. It does work pretty hard.
Take off the post-motor filter (Clip on cover underneath the dust bin). If it's heavily blackened, that's a good clue.
The bad news is that a new motor and a new post-motor filter would set you back about £60, by the time you include VAT and shipping, even off t'Internet.
The good news is that Dyson offer a fixed-price at-home service for £65, including any necassary parts.
The motor in my machine failed a few months back. I found the Dyson service deal on the website, filled in the form on the support page one Thursday evening, had a call back on Friday, setting up a visit for Tuesday the following week.
The guy came and as well as a new motor and filter, he fitted a new clutch assembly (he said 'cos the old one looked a bit worn), a new pre-motor filter, new belts and a new cyclone assembly (I have a feeling there was a safety redesign: The new cyclone has a lock that prevents you releasing the cyclone inadvertently if you press the release button whilst lifting the vacuum by the handle on top of the cyclone)
So there you are: for a fiver more than the cost of a new motor and filter, I had about £120+ of bits fitted and guaranteed for a year.
I'm sure this has been posted in reply to several other Dyson motor failures - you may have found an answer much quicker.
No matter - Was that helpful?
John, April 2008