To replace an air conditioner filter, remove the filter, determine what type of replacement filter is necessary and slide it into place. The filters in window units should be replaced yearly and cleaned once per month.
For household air conditioner units, the first step is to locate the air filter. If the air filter is located behind the main vent that blows cool air, there is probably a set of fasteners holding it in the housing, which needs to be removed. Some air filters are located in a slot in the furnace, and they can be removed manually after the furnace has been shut down completely.
The next step is to buy a replacement filter. Fiberglass filters should be replaced once per month, and they look similar to a window screen with a larger frame. If the filter is rectangular, approximately 1 inch in width and has diamond patterns, it may be a pleated filter, which needs to be replaced every 90 days. If the filter looks similar to a pleated filter, but is roughly 4 inches in width, it is probably a media filter, which lasts for up to one year. It may be necessary to check with the manufacturer to determine the proper filter type.
The final step is to place the new filter where the old one used to be. It is important to follow the directions and guiding arrows to make sure that the filter is installed the correct way. The filters in window units are located behind the vent that blows cool air, and they can be switched out annually in a similar manner to household units.