The house
How to Set a Thermostat So the House Cools Evenly
A setpoint the system can hold, fan on auto, and why closing vents in empty rooms makes the problem worse.
A thermostat does not make cold air. It asks the equipment to run until the sensor is satisfied. If the sensor is in a hallway and the bedrooms face west, the hallway will be comfortable and the bedrooms will not.
Settings that help
Fan on auto, not on. 'On' stirs air that has not been cooled and can make the house feel clammy. A setpoint you can hold, often 74 to 78 in a humid climate, instead of 68 that the equipment will chase all day.
A schedule that starts cooling before you get home works. Dropping the setpoint five degrees at once does not make the equipment larger. It just makes it run longer.
What does not help
Closing vents in unused rooms. The air has to go somewhere. Closed vents raise pressure, freeze coils, and leak into the attic. If one room is always hot, the duct to that room, the insulation, or the window is the problem. A thermostat in the wrong room will not fix it.
If the house was even and now it is not, something changed: a filter, a failed damper, or a system that is icing. That is an independent AC repair question, not a lower number on the wall.
Ready to call a shop? Find independent AC repair by city.