The desire to cool the air by artificial means is symbolic of your ability to regulate such elements of life at your own whim.
The larger the air-conditioning unit, the greater the sense of control that is being expressed. In this way, a window unit is reflecting a modicum of control, whereas central air relates to a more comprehensive desire to rein in your passions.
If the air conditioning is broken, such a dream relates to the inability to keep cool under pressure.