Power steering loss, lights dimming.

My Rio LX has been squealing for a month or so now, I took it into the shop and they said they checked everything, and found that the mount for the alternator was stripped, and they rethreaded and mounted the alternator. They also said they checked the pulleys, power steering pump and system. After I got the car back, the issue went away for about a month, but now the problem is back. The power steering fluid is full, and colored fine, the power steering belt is brand new, the other two belts are about 15,000 miles on them, at least that's what the dealership claims. The problem usually comes up when it's cold, but it also happens on normal days when I turn the wheel all the way over. Before I took it into the shop, the belts all stopped when I turned the wheel all the way over. That hasn't begun again yet, but the pump makes a hissing or sucking sound and the hose leading to the reservoir tightens up now. I also have steering wheel vibration while on the express way, no connection to speed, but it feels like the wheel is switching between extremely hard to turn and extremely loose.