Preparation

• Disconnect the power to the central air conditioning system. You will find the circuit breaker to the unit inside your home's electrical service panel. You will need to purchase a filter for your inside unit. Wear gloves and eye protection when working on any equipment in your home.
  
  

Maintaining the Outside Unit

• Clear away plants from the outside unit. Leaves and debris that builds up close to the unit will prevent it from working efficiently. Use a screwdriver to remove the shield that covers the fan--it is held in place by four to six retaining screws. Apply a few drops of electrical motor oil to the fan motor's lubrication ports if your unit has them.
  
  Inspect the drain and make sure that there is no standing water. A clogged drain will hamper the efficiency of your air conditioner and could leak water into your home. If you notice an accumulation of water, clean the drain.
  
  Spray the coils with air conditioner cleaner. Allow it to sit for a period recommended by the manufacturer, then spray off the fins and coils with a garden hose.
  
  

Maintaining the Inside Unit

• Remove the cover from the air conditioning unit by removing the two retaining screws at the top and lifting off the lid. Inspect the blower area and vacuum the dust and debris from inside. Vacuum around the inside unit as well.
  
  Replace the filter by unclipping it and sliding it out. The new filter will slide back in and will be locked in place with the clips. The filter may not require clips, depending on your model. Inspect the drain line that attaches to the side and runs into a pan below the unit. There should be no water standing in the pan. If there is standing water, the drain will have to be cleaned.
  
  One way to keep the drain clean is to pour a 50/50 solution of bleach and water down the drainpipe from inside. The bleach solution will help keep algae and mildew from building up inside the line.