A central AC system's air compressor and condenser are usually located outside the house, close to your foundation. It works best when there's about 24 inches of clear space in all directions, so get rid of nearby shrubs, tall grass, leaves, and hanging branches.
"Install condensers or window units on the north or east side of your house, or build a screen to shield them from the sun. Putting them in direct sunlight reduces their efficiency by as much as 10 percent."
—Richard Trethewey, TOH Plumbing and Heating Expert