Intermittent lack of PAS

[calman]

My daughter has recently purchased a 55 reg Focus 1.6 Zetec petrol, a very good clean car with a decent history. The only major problem seems to be the occasional loss of power steering. The car has very recently had a brand new PAS pump fitted with a new PAS sensor switch so it seems strange that she looses PAS. I did re-route the wiring to the switch as this had been fitted incorrectly and was stretched over a hose. This has not made any difference as the problem re-occurred a couple of days later. Is there another fault possibly elsewhere? Surely if the rack was at fault then the problem would happen every time rather than intermittently?