How do you know when your home air conditioning needs freon?

There are many reasons why an air conditioning unit does not work well: its temperature control may be set too high; it may have lost all its refrigerant because of a leak in the system; its compressor pump may have stopped working; etc...

If you cannot see anything obviously "set wrong" the best advice anyone should give you is to call a licensed Heating, Ventilation and Air Conditioning (HVAC) technician to advise you and/or fix it for you.