I recently bought a Dyson 14 and needed to replace the carpet beater bar. I think I have accomplished this but when I turn on the vacuum it makes a terrible noise and the carpet/bare floor knob will not stay on carpet. (It pops past it). I am not sure what is going on. Any ideas? Hopefully just a small adjustment needed. Any help is appreciated.

Yea. Easy fix.

1. you installed brush incorrectly
2. clutch belt is twisted
3. the caps at the ends of the brush are not facing the correct way
4. sole plate is installed incorrecly.