My AC goes on and off

Patrick, you figured out this properly ! there is a sounds involved into this hole story, but this sound (squealing belt sounds) happens only on cold engine in the morning when I put it into reverse. But when I start to drive it forward it goes away ! also when I reached to a mechanic to check it (not AC guy) it did not happened on warm engine (but the AC goes away when it's warm), so he just oiled some pulley and there is no error code thrown or anything obviously wrong. Thanks for your prompt response.