Power steering

I have a Mazda 3 2005 and the dashboard lights, the AC and the radio will shut off, then my power steering will go off. Sometimes, it shuts off for a good while, and sometimes it just shuts off for a few seconds to a few minutes. We thought it was the water pump, but we took it to Pep Boys and they went to go switch out the water pump and they said it looked fine and so they said to take it to a dealership. I just wanted to get an idea of what may be wrong with it and what it may cost to fix? The Air bag light will also take a while to turn off at first when I turn on my engine. I don't know if that is relevant or not.