2004 Optima V6 EX - A/C problem

Hello, It sounds like the step being missed is that the A/C unit needs to be vacuumed before adding refrigerant and oil. The refrigerant system is only filled after enough vacuum pressure is placed on the system, and attempting to fill it with refrigerant from a can will only work until the pressure in the can is the same as the pressure in the system. In other words, and in theory, about half of the can should be sucked into the refrigerant system before it will take no more. Also, I see this situation time and time again. Replacing parts, at this point, has likely cost more than a diagnosis and recharge, so my advice is to have it diagnosed before incurring more cost. If you have replaced the faulty component, the good news is that a vacuum and refill should make it function, but the issue might have just been a bad sensor or a leak.