sorry to dig up an old thread but I just had my truck in due to some hard steering which would ease up and then get hard again when turning. Fluid was changed with the recommended mercon every 30,000 miles. I now have 82,000 miles on the truck and the shop told me that I needed a new power steering pump, rack and pinion, and lines due to the fittings being all rusted. I picked up the truck today and the darn thing started growling at me and then the steering got hard again, especially at low rpm's. They are now saying it could be a bad reman'd pump (a1 cardone) or the pressure switch in the line. I trust this place as I used to work there and know the guys pretty well so I don't think they would screw me. Im just getting aggrivated as I am now at $1400 and am refusing to pay anymore since they were supposed to diagnose it and fix it the first time.

What does that switch that screws into the pressure line do exactly? Does it make a light come on the dash or shut down the system?