It is not necessary but it is recommended. If you do not vacuum it you may have some air or water in the system that will eventually end up diluting down the new system.
Yes, of course vacuum is required before gassing.No vacuum, implies that the gas will not move as the pressure inside and outside would be the same.Thereby, no cooling
Yes it is necessary to vacuum an ac system, because if you don't it may cause future problems and possibly clogging. So if you are thinking about buying an ac system make sure to vacuum it so you can get the most out of it.
yes. Before filing the refrigerant, an A/C system will be placed under vacuum to remove the moisture contents and dusts in the pipe lines. A vacuum pump is used to create the vacuum and removes the moisture in the form of vapour.
