Winter’s tough enough without your furnace dying or not putting out enough heat. And when it comes to furnaces, an ounce of prevention truly is worth a pound of cure. So here are some basic maintenance tasks that you can do to ensure that your natural gas or propane-fueled furnace stays running in peak condition all winter. Together, these tasks will take you less than three hours to do, cost only a few dollars, and require a few basic hand tools. That’s pretty cheap insurance for a worry-free winter of cozy, cost-effective warmth.
By the DIY experts of The Family Handyman Magazine:February 2012
Flip the electrical
power switch to “Off.”
Remove the combustion chamber door by lifting up and pulling it
out, and remove the burner cover (if you have one). It’s usually
held in place by two screws.
Turn the power switch on and activate the burners by turning
up your thermostat. Inspect the burner flames. The
flames should be fairly even and blue. Yellow flames indicate
dirty burners. (Don’t breathe on the flames because the extra
oxygen will also make them turn yellow.) Don’t adjust the burners
yourself. Call in a pro.
Turn off the power switch again and shut off the gas
by giving the valve one-quarter turn. Vacuum the burners and
the furnace base. To get at the back of the burners, tape a 20-in.
length of 1/2-in. drain line to your vacuum hose. Vacuum everywhere
you see dust. While everything is open, use a flashlight to
look for signs of soot (fine black powder), which often indicates
poor combustion. Lift off the lower door
(blower door) and vacuum the blower compartment.
Remove the blower (also called a squirrel cage) in order to
clean it. If you have a control panel in front of the blower,
two screws will loosen it and you can let it hang. Next, using a
7/16-in. socket and ratchet, remove the two bolts that hold the
blower in place, then gently lift it out.
Clean the blower blades thoroughly with a vacuum and small
brush. Take care not to stress the wiring or disturb the
counterweights that will be on the fan blades. If you can’t clean
the blower thoroughly, don’t clean it at all; you could throw it off
Change the furnace filter every one to three months. A $1
fiberglass filter will adequately protect the blower and blower
motor. If you want to install a more expensive, high-efficiency filter,
check the owner’s manual for the manufacturer recommendations.
High-efficiency filters can restrict the airflow, strain the
blower motor and make your furnace less efficient. If you want
cleaner air, the best option is a separate air-cleaning system.
Blow dust off the pilot. Direct air to the exact spot by blowing
through a drinking straw. A dirty pilot can cause the flame sensor
(or thermocouple) to get a false reading that the pilot isn’t lit. Some
newer furnaces have hot surface igniters instead of pilots and electronic
The flame sensor occasionally becomes coated with
residue and will prevent your furnace from lighting. Remove
it by pulling it down out of its bracket. Lightly clean the surface
with fine emery cloth and slip the sensor back into its bracket.
Hot surface igniters are the most common ignition
system on furnaces being manufactured today. They take the
place of standing pilot lights and electronic igniters. Clean the
dust off the hot surface igniter by leaving the igniter in place
and blowing air through a straw. This part breaks very easily;
don’t even touch it. In fact, when you replace the furnace doors,
do so gently to avoid breaking the igniter.
The belts on belt-driven blowers need occasional adjustment
or replacement. Inspect the drive belt for cracks or
frayed areas. A new belt costs about $5. When you install the
new belt, tension it so it deflects 1/2 to 3/4 in.
Some older furnaces have two motor bearings and two
blower shaft bearings that require annual oiling. Clean
around the oil caps and remove the caps. Apply two to three drops
of lightweight machine oil and replace the caps. Don’t over-lubricate!
If your furnace heating ducts also serve as air conditioning
ducts, they may have dampers that require adjusting for
seasonal changes. The seasonal settings should be marked. Two-story
homes often have separate supply trunks to serve the upstairs
and downstairs. To send more warm air downstairs (winter setting)
or more cold air upstairs (summer setting), adjust the damper
handle on each supply trunk.
Seal leaky ducts, especially return air ducts, with special
metal tape or high temperature
silicone. Then conduct a backdrafting test
to make sure the combustion gases go up the flue: Adjust the
thermostat so the burners come on. Hold a smoking stick of
incense beside the draft hood. The smoke should
be drawn into the hood. Also inspect the exhaust vent pipes on
your furnace and water heater (while they’re cool). White powdery
residue can indicate corrosion. Call in a pro to fix these problems.
Have the necessary tools for this DIY project lined up before you start—you’ll save time and frustration.
Avoid last-minute shopping trips by having all your materials ready ahead of time. Here's a list.
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