How do you evacuate the entire AC system of freon and pressure before recharging?

To evacuate the AC system of freon and pressure, first, connect a vacuum pump to the service ports of the system using appropriate hoses and fittings. Open the valves to allow the refrigerant to flow into the recovery machine, ensuring that the system is completely emptied. Once the refrigerant is removed, run the vacuum pump for about 15-30 minutes to eliminate any moisture and air from the system. Finally, close the service valves, disconnect the pump, and the system is ready for recharging.