Take the AC and alternator belt and try spinning the pulleys individually to find out which one could be be screaching. Increased rotating resistance may be found in the pulley that is screaching. Make sure to check the AC pulley before taking off the alternator belt. If it's the AC, it may save some trouble shooting work.
The engine can be switched on for a short period of time without the belts to eliminate the possibility of the engine.
Remember, before starting, to have a reference of how the belts run. If one can't be obtained, take a digital pic of it and print it out, or draw it out.
Good luck with with the trouble shooting method and / or finding a suitable mechanic
I hope this helps