If you live in a region that has cold winters, it is best to remove the AC and store it indoors. If you live in a region with mild winters, you can leave the unit in place but you should purchase an air conditioner unit cover (like the Classic Accessories Veranda Air Conditioner Cover) for protection.
By following the steps below for maintaining your window air conditioner, you can save money and extend the life of your system.
1) Take the air conditioner out of the window. After you ensure the power cord is unplugged, unscrew the side panels and prop the window up with a shim. Window units have most of their weight in the back, so they will tend to fall toward the outside when you open the window. Ask someone to hold the appliance steady when you are ready to open the window. Take the appliance out from the interior of the room and put it on a solid surface that provides enough room for you to work.
2) Remove the air filter and clean it using water and soap. Rinse away the soap and leave it to dry. If you see any damage to the filer, purchase a new one online or at any local home improvement center. While the filter is drying, vacuum out the area inside the AC around where the filter is installed.
3) Remove the outer housing and wash the outside and inside surfaces of the cabinet to remove dirt, dust and debris.
4) Clear out any debris inside the cabinet. Check all the corners so you do not miss anything. If possible, turn the cabinet upside down and let the debris fall out.
5) Use a mixture of warm water and soap to wipe down all non-electrical parts and inside surfaces. A paintbrush is a good tool for this job. Be careful not to get water on any electrical pieces because moisture will damage them.
6) After cleaning the interior with soapy water, cover all electrical components with plastic and use the garden hose to spray down the appliance. Spill out any standing water, uncover the electrical part and let it sit out to dry for a minimum of 24 hours.
7) Before putting the AC back together inspect the evaporator fins. The fins should be straight and parallel to each other. The unit will not work efficiently if the fins are bent out of shape. Home improvement centers carry inexpensive fin combs you can use to straighten them out.
8) Cover your window air conditioner with plastic and locate a safe place to store it. If you prefer to keep it in the window during the winter, cover it with waterproof material. Close all the vents before storing for the winter and seal any openings around case.