How To Clean a Furnace

The furnace filter should be replaced or cleaned at the beginning of the heating season and about once a month during periods of continuous use. To check the filter, take it out and hold it up to the light. If it looks clogged, replace it with a new filter of the same type and size regardless of the length of time it has been used.

What You'll NeedYou'll want to have these tools on hand to clean a furnace filter: Screwdriver Replacement filter Toothbrush Vacuum cleaner Clean rags

A disposable furnace filter consists of a fiber mesh in a cardboard frame. The size of the filter is printed on the edge of the frame. An arrow on the edge of the frame indicates the correct direction of airflow through the filter. Air flows from the return-air duct toward the blower, so the arrow on the filter should point away from the return-air duct and toward the blower.

A permanent filter is usually sprayed with a special filter-coating chemical, available at hardware stores and home centers. Clean this type of filter according to the manufacturer's instructions, which are usually attached to the furnace housing. Here's how to replace a filter:
 
Step 1: Look for metal panel on front of furnace below return-air duct, between duct and blower system. Panel may be marked filter, or it may form lid or front of boxlike projection on furnace housing.

Step 2: Slip panel off its holding hooks, or unscrew panel from box or furnace housing. On some heating units, filters are exposed; just slip filter up and out of U-shape tracks that hold it in place.

Step 3: Inspect and replace or clean filter, depending on type.

Step 4: Clean blower assembly, belts and pulleys to blower, and motor housing. Cleaning blower is critical if furnace has a squirrel-cage fan, because openings in this type of blower often become clogged with dirt. To clean blower, remove panel that covers filter to gain access to blower or panel on front of furnace. This panel may be slip-fit on hooks or held by series of retaining screws. Access to inside of blower is usually gained by sliding out fan unit, which is held on track by screws.

Three parts of the air-moving system should be kept clean: the filter, the blower, and the blower motor.

If power cord to fan assembly is not long enough to permit fan unit to slide all the way out, disconnect cord. Mark wire connections first so you'll be able to reassemble unit correctly. With toothbrush, clean each fan blade and spaces between blades. Then, with vacuum cleaner hose, remove all dirt and debris loosened by brushing. Vacuum belts and pulleys. Wipe motor housing clean to prevent heat buildup in motor.

Sealed blower motors need to lubrication, but if yours has oil ports, learn how to service them on the next page.

• How To Repair Gas Furnaces and Gas Heaters: Gas furnaces have become popular because they burn fuel cheaply and with few problems. Keep your gas furnace running trouble-free.
• Major Appliance Repair: If the furnace isn't the only thing in your house on the fritz, you can learn how to fix other machines in this article.
• Small Appliance Repair: Once you've tackled the furnace, a toaster or blender seems like child's play. Find out how to fix them here.
• Thermostat Maintenance: To make sure there's actually a problem with your heating system, you may want to check the thermostat, too. Learn how to calibrate a thermostat.