Found it on Volvo site. Interesting reading about the magnet....
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Power Steering Fluid Cleanliness. I keep inside the power steering fluid reservoir a small but VERY STRONG magnet. I lowered it down inside on a wire and because it is strong it attaches to the metal bracket holding the reservoir. After first two weeks I was cleaning it every second or third day and you would be surprised how many metallic particles it was able to take out. For the first week the magnet was all covered and black every time. Now my power steering fluid is so clean, that I can see the bottom of the container with a flash light. Of course I changed the fluid after I take most metallic particles out. Besides there was a bulletin issued by Volvo stating that inside PS container there should be a magnet.
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Power Steering Fluid Change. [Tip] If you want to drain the system, loosen the fittings at the steering rack, from the pump & reservoir, let all the fluid drain out, then refill system with Volvo steering fluid, or Dexron. Auto trans fluid will aerate more than the steering fluid, so you will get less steering wheel chatter, when you start the engine & drive the car. Fill the reservoir, then start the engine. When the pump empties the reservoir, then refill it.
[Another Procedure: Query:] My power steering fluid looks pretty bad. What's the best way to replace it - without disassembling the entire system? [Response 1: Steve Ringlee] The return hose to the p/s reservoir is the top hose. Disconnect this at the reservoir (see Editor's Note below) . Using a small piece of solid pipe, clamps and some clear vinyl tubing, make an extension that will direct the fluid into a container or bucket. Get a quart of new fluid (I use Mobil 1 synthetic ATF, which works fine even though your manual calls for Type F.) Start the car and have a friend cycle the steering wheel back and forth. As the pump moves the old fluid out the hose, refill the reservoir with new fluid. When you've just about used up the quart, you will have completely flushed out the old fluid. Re-connect everything, bring the reservoir up to level and you are back in business. If you suspect metal contamination in the old fluid, place a strong magnet on a thin wire into the reservoir and leave it there for a week, removing it to check it and clean it off. [Response 2: Jerry Andersch] One other bit of advice. Be careful not to be overly aggressive in removing the return line to the plastic P/S reservoir. Lines that have never been removed can be tough to free up. Resorting to yanking, twisting, and swearing can result in a unexpected trip to the wrecking yard to find a replacement reservoir. Easy does it and save yourself some grief. [Editor's Note:] The return line is VERY TOUGH to remove because of an aggressive barb at the end of the outlet pipe. Be prepared to cut about one inch of hose, enough to peel it off the reservoir, so make sure you have a little extra hose you can pull up from the pump. To make life easier next time, file off the sharp edge of the barb to make the hose removable. [Response 3: Gary DeFrancesco] In my car, the oil was never changed by the PO, and it was black. Be prepared to dump in more than a quart of new ATF while flushing. The flow rate through the pump surprised me, even at idle. I went through 2 quarts of oil as fast as I could dump it in. And I mean DUMP. Have a friend or spouse start the engine and turn the wheel lock to lock. I found it best to do this with the front wheels off the ground. Have your partner start turning the wheel as soon as the engine starts since it will not take too long to go through the ATF.