Q: What would cause a loud squeal inside ac air compressor at start up? on 1992 Mazda 929

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Mechanic replaced belts with water pump. Sound comes from inside air compressor.
(2) Answers
(2) Comments
Can the bearing be checked and replaced or will the compressor have to be replaced. Thanks for your help by the way.
Did the squeal start BEFORE OR AFTER the 'belts and water pump' replacement? Does the noise only happen (or happen worse) when A/C is on? Are belts good grade , and properly tensioned ? OR I could be WAY off base and the compressor's screwed. I hope not for your $ sake. Good luck.
Even with AC off the squeal happens most of the time when I start the car. We took it back to the mechanic after the belts and water pump were replaced and he said the noise was not the belts that it was coming from inside the ac air compressor. Air compressor was replaced 2 times before the fuel pump went out (second time for the fuel pump too). We found a new mechanic after the shop that replaced the fuel pump and compressor twice. The second mechanic replaced the belts and the fuel pump, and then the squeal started. Compressor makes different noise when ac is running, sort of like a low grinding noise. Also thanks to you for your help.