Squealing when you turn the wheel to go around a corner is almost always because the belt is sliding over the pulley on the power steering pump. This may be because your pump is dying (the bearings in it are getting stiff and causing drag, or other internal problems). It may also be because the belt is worn out or contaminated (say, by an oil leak) and slipping as a result, or there may be a tensioner on the belt that needs adjustment or needs to be replaced. Usually it's best to start by examining the belt and tensioner, and replacing the belt with proper tensioner adjustment.
You also mentioned a strange noise when your climate control is being used, and you said you've replaced the belts and tensioner. If you're sure that the correct belts are installed and the tensioner is set correctly (it's easy to set some tensioners far too loosely in my experience), you may want to check each of the ancillaries driven by the belts - the alternator, A/C compressor, steering pump, etc - any of them putting extra drag on the belt could be causing it to slip. Sometimes, this can be done easily - take the belt off and try to rotate each unit by hand, and see if any of them obviously feel bad. Also, if the belts run over any idle pulleys, make sure the pulleys are in good shape and aren't worn or slipping.
