The brush will not turn. It makes a grinding

Is it when you go from carpet to floor or floor to carpet? It will make a loud noise detecting a possible suction issue. I've also had loud noises and turned over the vacuum and where the brush is, traps hair, thread, rubber bands, etc. Just take a scissor and cut it all out. Don't cut the bristles. Roll the brush as you cut and pull all the stuff wrapped around the brush. Once it is free, try it again.

Hi, sounds like you need a new belt or brush and bearings . Sometimes when a belt goes it makes a bad noise as one of the belt teeth make be worn out. Hope this helps.

It is probably the brush roll motor making the noise. Remove the brush roll & belt and turn both motors on. If you do not hear the noise when both motors are running the noise is likely coming from the brush roll

go to http://www.dyson.com/support/help.asp?article=2
select your model, and see the guide troubleshooting , proceed with common sense. and fix it.
God bless you
Sometimes you must check noise, from bloackage, debris, dust, or fan blades motor, test it.

The cog belt is probably not aligned with the motor gear. Watch this video and follow its instructions closely.

Did you check the roller brush to make sure it was clear of debris?

You really need to take the sole plate back off and make sure the belt is running exactly where it's supposed to go and not looped over a piece of plastic or anything. More important is that you make sure the ends of the brush are seated properly and the bearings the brush is mounted to are clean and rotate freely. Look at each component and make sure they are assembled perfectly. Make sure a plastic ring or piece that goes on the end of the brush didn't get dropped under a piece of furniture and you forgot about it. If the problem keeps happening, take the brush and belt back out and carefully turn the machine on to see if it makes the sound. If it doesn't make the sound with the brush out, the problem is with the brush assembly. If it does make the sound, the clutch that turn the brush on and off is damaged and needs to be replaced. You can order a new clutch assembly and replace it without much trouble. They want you to think you can switch between floor and carpet settings all the time but it's really really stressful on that clutch to switch between settings with the motor running. Think about how powerful that motor is. Think about the poor unassuming brush assembly being jerked to life by that powerful motor running at full speed. I've seen that destroy a clutch in about two years. Anyway, it's much better for the life of your dyson to turn the motor off when you switch to carpet mode (when you turn the brushes on). You probably don't have to bother turning off the motor when turning the brushes off, or switching to bare floor mode, because it's not that stressful on the mechanism to just disengage the running motor.

On a Dyson this engages the brush bar. Two possible faults: Debris (hair etc) caught in brush bar - cut out with knife. Or - damaged drive belt - pieces of belt striking casing. Last, but unlikely cause, debris in bearings of brush bar - replace brush bar.

http://www.fixya.com/support/r4530769-diagnosis_fix_hoover_steamvacs_when

you will probably have a faulty roller bar take of panel on bottom of vaccum. Now remove the roller bar hold the bar by both ends and try spinning. This should be easy and smooth if not pull off the end cap these will be very tight and check the bearings in each end i think you will find a few small metal balls rolling around inside if this is the case you need to replace the bar