How to Replace an Air Conditioner Filter

Lead Image
  • 1-2 hours
  • Intermediate
  • 15-30
What You'll Need
Replacement air filter (fiberglass, pleated, or media)
Damp cloth (for cleaning filters for window units)

The air conditioning unit in your house is one of those things that you may only notice when it stops working. In order to keep from reaching this sort of impasse, or at least making it less likely to happen, you need to perform regular maintenance to make sure the internal parts are clean and in good working condition. The most basic maintenance you can perform is cleaning or replacing your air filter, and here we will cover several ways to do this, depending on the layout of your cooling system. With proper maintenance of your air filter, you will be able to save yourself a considerable amount of money and time spent sweltering in your uncooled home because you need to call in a repair service to fix it. (For window units, skip the following three steps and see the end of the article.)

Step 1 - Locate and Remove Filter

Some may be located behind the main vent that lets out cool air into your house, in which case you may need to pull back a set of fasteners to remove the filter from its housing. This vent is usually located by the thermostat. In other cases, the filter may be located in a slot in your furnace. Before removing the filter, make sure to turn the unit off for safety's sake. Furnace units that use larger media filters will have them behind a filter cap, a metal or plastic housing that can snap off by hand. Once you have found the filter, making sure no air is going to pass through the system while you work, remove it.

Step 2 - Identify your Filter Type

For all but the window unit, you will need to determine the type of filter and its dimensions before you buy a replacement.

A fiberglass filter resembles a window screen with a larger frame. This is an older type of filter and needs to be replaced at least once a month.

A pleated filter is rectangular and about an inch wide. It should be replaced at least every 90 days, but HVAC experts recommend 45 days.

A media filter resembles a pleated filter, but is about four times as wide. It should be replaced every six to eight months, but in some cases can last up to a year.

Step 3 - Install the Filter

Once you have the correct unit for your air conditioner, slide it into place. There should be an arrow telling you which side to put it in first, and it is important that you follow this as the filters are designed to work this way. Put the filter cap back on or refasten the grate. It is now safe to have air flowing again.

Window Units

For window air conditioning units, the filter will be found directly behind the place where the cool air comes out. Window air filters only need to be replaced about once a year, but they should be cleaned monthly, depending on how often you use the air conditioner.

Turn off the unit and locate the filter. Take it outside and gently but firmly knock it against a flat surface, which should release a good deal of collected dust. Take the damp cloth to the filter and lightly wipe it down. Allow it to air dry or dry it with a towel, as placing a wet item into any kind of electrical system is a bad idea. Put the filter back into your wall unit. It is now safe to use again.