If your air conditioner isn't leaving you cold, it could be time to do some troubleshooting. Central air conditioning units need regular maintenance to work efficiently. First, check to make sure the filter and condenser are clean; dirty condenser coils can be brushed or vacuumed. If the system leaks water, a clogged condensation drain is likely at fault.  And if the unit runs but doesn't cool, the refrigerant could be low -- a condition that is easily repaired by a service professional.