Why is my window air conditioner blowing air that is cool but not cold like it used to?

There are many reasons why it does not work like it did before: someone else may have turned the temperature control up higher than it was set before; it may have lost some of its refrigerant because of a leak in the system; its compressor pump may not be running properly; etc...

If you cannot see anything obviously "set wrong" on the controls of the ac unit, 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. For personal safety reasons only technicians who are licensed to work on HVAC (Heating, Ventilation and Air Conditioning) should do this kind of work because they have the right test equipment and tools and have been trained in how to do this work safely.