I want my house to get cooler. The air conditioner I have puts out air thats 60 degrees F or 15C at the floor register. My house never gets colder than 75F or 24C. If I run the air conditioner all day long it never gets colder. I have lots of windows in the house which I have blinds on to stop the sunlight. Is there anything I can do to have a colder house? My air conditioner is 3 years old, is there any maintenance I need to do?