Window unit air conditioners (ACs) typically do not need to be drained before charging them with refrigerant. Window units are pre-charged with refrigerant at the factory, and under normal circumstances, they should not require additional refrigerant during their lifespan.
If a window AC is not cooling properly or is not functioning efficiently, there may be other underlying issues causing the problem. Some common reasons for poor cooling in window AC units include dirty air filters, blocked vents, and problems with the condenser or evaporator coils.
If you suspect a refrigerant leak or any other serious issue with your window AC, it's best to contact a qualified HVAC technician to diagnose and repair the problem. Handling refrigerant requires specialized equipment and training, so it is not recommended for homeowners to attempt to charge or repair the unit themselves.
In summary, you typically do not need to drain a window unit air conditioner before charging it with refrigerant. If your window AC is not functioning correctly, it's best to seek professional assistance to identify and address the root cause of the problem.