Steering Intermittent sticking (Vectra C – 56)

[Alhazard]

Hi
I have a problem with my steering, car is a 2.2 Sri on a 56 plate.
Best way to describe it is you turn the steering wheel, it sticks and get’s really tight (almost as if there’s no power steering).
What makes it more annoying is the more it it sticks and the tighter/heavier it gets the more the steering wheel squeaks.
Sitting on the drive steering both ways to full lock absolutely fine (no squeaking either).
I’ve changed the power steering fluid, checked the battery voltage & checked for play in what I think is all mechanical steering components and so far nothing, can’t find any leaks either.

I’m totally stumped, it’s fine sitting on the drive and on the motorway.
No warning lights showing.
Turning while going up and down hills it gets worse but does not happen all the time.

Is there anything else I can check?

Thanks

[alcutler]

Have you checked the alternator output - should be around 14.4 volts with the engine ticking over - also the electrical connections to the pump itself - any warning lights on dash?

[Alhazard]

With engine ticking over it's 15v, electrical connections looked fine to the pump, no warning lights on the dash either.
Thinking I might just bite the bullet and take it to a garage.

[m8internet]

Sounds to me like the Pump itself has failed, and is unable to operate at high speed (when it has to do the most work)