Heating and cooling systems must be properly maintained for the best efficiency and worry-free operation.  Central air conditioner or "split systems" are so named because they have components that are in separate locations, or "split".  A split system will have a furnance, a circulating fan, and an evaporator coil located in an interior closet or attic.  They are connected to a condensing coil located on the exterior house by refrigerant lines.  Heat pumps produce heated and cooled air.  They are almost identical to condensing coils, except they work with an air-handler inside the home instead of an evaporator coil and circulating fan at a furnance.  The components are different, but the function is the same. 

Whether a split system or a heat pump both must be maintained.  The evaporator coils and condensing coils must be kept clean for optimal performance.  The filters must be changed regularly.  If the filters become clogged the air flow will be greatly reduced and thus the performance will be affected.  Filters come in many different sizes and types so ensure that your filter is the correct type and size for your system.  Have your entire system checked at least annually by a qualified HVAC tech.  Maintenance agreements are available and provide the best early warning approach for a trouble-free system.  Trust me, waiting for a HVAC tech to show up when the outside temperature is over 100F is no fun.

Here are a few other tips:

1. Keep the area around the furnance and coils clean and debri free, this includes cutting back scrubs and trees from the condensing unit.
2. Change firlters regularly, such as monthly, quarterly.  Keep a log.
3. Stay aler for any unsual noises or smells coming from the system when operating.
4. Becareful not to damage the condensing unit coils by flying rocks from the mower or hitting with the weed wacker.
5. De-energize the system before attempting maintenance or repairs.
6. If you see water dripping from a plastic pipe discharge below the soffit of your home.  Call an HVAC tech to check the evaporator coil in the attic.  There could be a problem.
7. Schedule annual or bi-annual professional service.