"If the air isn’t seem cool enough it is recommended to use a thermometer to check the difference in temperature between the air going into the unit and the air being blown into the room. Normally, the temperature difference should be more than 15 degrees. For instance, if the temperature going into the air conditioner is 70 degrees, the temperature coming out of the unit should be at least 55 degrees or less. If the difference is 15 degrees or more there is probably no cause for concern. If the temperature difference is less than 15 degrees you should check the following: Back cover Air damper Condensing coils Check to make sure the air damper is closed. If it's open, it will bring in outside air and reduce the efficiency of the air conditioning unit. During the winter time lots of people cover their air conditioners to protect the unit from the weather. In the spring or summer they will sometimes forget to remove the cover. If your unit has a cover on the outside portion of the air conditioner remove the cover first. The condensing coils will always be on the ""warm"" side of the air conditioner. That is, on the side that faces outside of the room to be cooled. Air is drawn into the back of the air conditioner on the sides through vent slots and is blown directly out through the condenser coils."