1997 Cherokee when ac is turned on the volts drop and belt squeels it has a new alternator water pump and belt?

First, check the status of the AC compressor. Make sure you can turn it by hand while the clutch is disengaged and the engine is off. You should turn it several turns, just to make sure it's free. If the AC compressor isn't turning freely it's most likely faulty. If it does turn freely, check the belt tensioner to make sure it has enough tension to keep the belts from slipping.