Air conditioner. Our air conditioner will be on for a couple hours and only change the temperature

Question

Our air conditioner will be on for a couple hours and only change the temperature a couple of degrees. With the heat increasing in the south, this is never racking to set the thermostate fro 73 degrees and after a few hours of running it the temperature is still 79 degrees. I don't know if this is the unit that we actually have, but do you have a round about idea of what could be going on?