Driver ac not cooling and passenger side takes forever to cool down but does not get very cold

https://www.youtube.com/watch?v=mS56WnGUSTU

https://www.youtube.com/watch?v=--SCk_gHM4o
This problem is a low freon charge in the system. ... But a system that is 1/2 pound low will cause the passenger side vents to blow cool or cold air, and the drivers side to be less cool or even warm on this car. There is simply not enough freon capacity in the system to cool the air to the drivers side. https://www.justautorepair.com/buick/century/cool-passenger-warm-driver

The 2 vents on the drivers side have warm air blowing out. ... But a system that is 1/2 pound low will cause the passenger side vents to blow cool or cold air, and the drivers side to be less cool or even warm on this car. There is simply not enough freon capacity in the system to cool the air to the drivers side.
https://www.justautorepair.com/buick/century/cool-passenger-warm-driver

There are 2possibles ,1. The heat / cool slide control is defective, it is not possible to repair. Most likely the servo motor that opens and closes the air vent that gives you heat or cool is stuck. Open your glove box and you will see 2 rubber tabs that hold the door at the open and down position. Push down on your glove box door until it swings all the way down (this wil be past normal open) up inside you will see a metal rod affixed to a arm that pivots via the servo left is full vent(cool) right is full heat. Push your hot/cold heat selector and see if it moves. It may not be moving its full extension. If your not sure push it right and you should get heat push it left and you should get cool check YouTube this is a common problem for this era of Buicks, good luck Bret

check the air vent of passenger side for any obstruction and secondly keep your thermostat full towards cold side make sure the ventilator is fully closed position and rotate the air selection knob clockwise and anti clock wise two three times than set it at the required position mainly your air selector seems to be malfunctioning there is nothing wrong with the ac

is300 has dual zone climate control
passenger side blend door actuater has probably failed

It sounds like the control motor switching from hot to cold is stuck halfway in between the two temp settings. You will have to take it down and replace it, it is mounted under dash passenger side near the blower motor.

if you have power there then the fuses are good or relays but if you have power then you ethier have a bad fan or ground wire also that fan should only come on when the ac is on

yes, check the freon level, its getting low thats why its working like that.

The air doors are controlled by actuators that on of them or so may need replacing.

What stuff did you put in it? You might need a freon recharge.