Whats Hapend To My Power Steering?

[weejimmy 1]

my power steering has gradualy got worse and worse and now dosent realy work at all

 

it started by not working when stationary and cuting in and out.

then started hapining while driving which was a bit dodgy as i would be puting effort into turning then it would work and id steer too much and go towards walls and stuff.

 

now it dosent realy work at all.

 

the belt is fine and theres fluid in it.

any ideas??

[brianthemagical 1]

Air lock or knackered pump/rack.