Window air conditioner units need basic service done to them or they will not work as well as they should. One of the more important things to be done is to clean the filter from dust and other debris that can block the air flow. When air flow is block a A/C unit can not work properly and can fail to cool a room as well as when it was new. How To Clean a Window Air Conditioner Filter Remove the fount cover. Each unit will have its own clips or unique way the cover is attached. Slide the filter out. The filter can be cleaned in a sink with water. Only use water as any chemicals that are used will circulate in the room the unit is in. After cleaning the filter simply install it back into the unit. Be sure it is aligned correctly so no debris gets past it while it is operating. How often the filter is cleaned will depend on the climate lived in. For example a desert environment has much more debris in the air than a high mountain region. Keeping the filter clean is very important since a A/C unit works with air flow to transfer hot and cold air to the right places.