How to Replace Furnace & AC Filters How to Replace Furnace & AC Filters
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How to Replace a Furnace, AC or Heat Pump Filter

Dirty filters are the number one problem when forced-air heating and cooling systems don’t work right.

©Don Vandervort, HomeTips

Position the replacement filter in the wall register with the airflow arrows pointing in toward the ductwork.

With a central forced-air heating and cooling system, air filters remove dust and allergens from the air before warming or cooling it and returning it to your rooms. For this reason, filters are critical components of these systems.

But, on the downside, as filters become clogged with dust and debris, they block the free flow of air, drastically reducing the system’s efficiency. Properly maintaining filters is an important way to keep your heating and cooling as affordable as possible. Replace or clean the forced-air system filters every six months unless they become clogged with dust sooner.

Filters may be located at the return-air registers in the home or in the furnace or AC unit’s air-handler cabinet. In many cases, they are in both places.

The first step is to turn off the heating or cooling system and then locate the filters and measure their sizes (or note the sizes marked on their frames).

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To replace a filter located in a room’s return-air duct register:

changing furnace filterSteve Heap /

Carefully unlatch grille’s cover and remove the dirty filter.

1Unlatch the register’s cover grille and swing it out of the way or remove it. Remove the old filter and immediately put it in the outdoor trash. Use a damp rag to remove dust from the grille and the surfaces of the register—both inside and out.

cleaning furnace filter grilleSteve Heap /

Clean dust off of the grille.

2Clean dust off of the return-air’s grille before installing the replacement filter. Be careful: The hinge side can easily unlatch on some types!


3Position the new replacement filter in the register with the airflow arrows pointed in toward the ductwork. Replace the grille and latch it. Mark the date on the filter’s frame so you’ll know when it’s time to change it.

replace furnace filter©Don Vandervort, HomeTips

Replace the filter with “air flow” arrow is pointing toward ductwork. Mark the date on the filter’s frame so you’ll know when it’s time to change it.

To replace the filter in the air-handler cabinet:

1Turn off the power to the unit. Look for the door or panel that conceals the blower; sometimes this is marked “Filter.” Lift this door or panel off of its holding hooks or unscrew its retaining screws to remove it.

2Check the filter. A standard filter is mounted next to or under the blower motor. Slide the filter out along its tracks. Check to see whether it is a disposable filter or intended to be cleaned and replaced—this should be marked on the filter’s edge, along with directions for cleaning, if applicable. If it’s a disposable filter, its size will more than likely be printed on the frame’s edge.

3Buy a replacement filter and slide it into place, noting the arrows stamped on the side that indicate the proper direction of airflow; be sure you face these toward the blower (away from the ductwork). Then replace the door to the cabinet.

The video below offers good advice for changing furnace and AC filters:

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