Vacuum is a process. Which exhausts from the AC Unit. Only Gas Run is in the entire AC. And cooling is okay. Vacuum is necessary for Refrigerator and Air Conditioner. When we Repair Refrigerator or Air Conditioner we should do Vacuum before charge gas. we should use vacuum machine for this process but some people use Compressor for this process. when we uninstall an we should Store his Gas in Outdoor Unit and when we install this AC another Place when we complete all Pipe connection then we should vacuum all Pipe and Indoor but don’t open Outdoor L Key before vacuum.
Vacuum Pump is Suck the Air . One line connect with vacuum suck side and his line second point connect with Outdoor gas charging point. then vacuum start you can watch video for vacuum.