Please what could be the reasons why my xc90 2005 model vibrates when I switch ON the AC and likely solution pls.

 

What engine do you have?

 

5cylinder engine

 

For a 5 cyl gas engine could be a worn serpentine belt, or problem with the tensioner. Those could be OK and the front of engine engine mount could be sagging and touching the frame (or left side of engine motor mount is flat) transferring the vibration of the engine to the subframe. - Perhaps most noticeable when idle speed might be slightly slower with ac on.