99 Camry making squeaky noise when turned left or right after changing belts.

Recheck the belt and belt tension.

== I have the same answer with perhaps a bit more description. Belt is slipping. I always use Toyota parts so that may help. Also you should use a belt tension gauge. Should be able to get the click type gauge inexpensively at NAPA. I have basically the same thing from Mercedes. But these click type gauges only work for narrower belts. For the alternator - A/C belt, the factory manual recommends the Burroughs belt tension gauge which is a different design with a rotating face. Found one on eBay for around $50. Both belts are ribbed so they shouldn't be slipping if installed correctly - especially if new, but slipping can glaze the rubber so if you find shiny spots on the belt, may be best to replace it again, they're relatively inexpensive. IIRC, power steering belt tension is around 80-100 lbs., for a used belt run at least five minutes. With the gauge you can dial this right in, and it's easy to be 30-50 lbs. off without one.

It's almost impossible to tension the belt with finger pressure against it. Automatic tensioners would have made things a lot easier, but that would cost Toyota money ;)

So check your belt tension, preferably with an inexpensive (~$20 at your local NAPA store) the Krit-it II gauge:

My preference is Gates belts and hoses. Unsurpassed research capability and quality (eg. world's first commercial PolyChain Carbon belt, strong as metal chains developed for Harley-Davidson just for the asking). IMO best in class.