Before the height of summer arrives, check your central air-conditioning’s exterior unit to ensure it is ready to provide you with maximum cooling while using the least possible amount of energy. First, confirm that the power is off. Then, check that the box sits level, and remove any objects or plants that may restrict its expulsion of interior heat. Remove the outside screen(s) and clean the fan, compressor, condenser coils and fins with a low-pressure garden hose. Before replacing the screen(s), check that the fan is unencumbered and that the aluminum fins are not bent. If necessary, you can gently straighten them with a butter knife or a fine comb. Next, go inside to replace your interior air filter(s), which can be accessed near the main fan. If filters are washable, clean them at least twice a year. Turn the power back on and set your thermostat to trigger the A-C operation. If anything is amiss, call for service now, to avoid the rush during the next heat wave. Be sure to ask your technician for a written inspection checklist.