Your mechanic cannot replace the pulley bearing?
Nope. He told me to bring it to air cond shop guy to check the problem first. Anyway, I just came back from air cond shop. Indeed the sound is coming from the bearing. Got it replaced and changed the gas inside the air cond system. Everything took like 3 hours plus. So far, it felt like the compressor is not draining as much power as it is before. But today is not a very hot day, so I'll see how it performs again on a hotter day.
This is the bearing.


cabut