Save money and increase your heating system's efficiency and comfort by following these simple steps to keep your furnace in tip-top condition.
Introduction
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. “The cost of a gas boiler or furnace tune-up averages $150,” says Mike Fisher of Homeserve, “while having to have an actual repair completed comes in at a much higher average of $450.” Many homeowners hire a pro to tune up their furnace when the cold weather approaches, but if you have a free weekend and a little acumen, you can save even the nominal cost of a service call with a DIY furnace cleaning.
According to HVAC specialist John Gabrielli, a service pro would conduct a thorough inspection of the furnace’s key components, including the thermostat, the vent system, the blower and all the safety features, and give everything a good cleaning. “A crucial step that should not be overlooked,” adds HVAC pro Jimmy Hiller, “is conducting a carbon monoxide test.” Altogether, this is a service you might want to pay for every three years or so, but on a year-to-year basis, you can do much of this yourself.
So here are some basic furnace 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.
Watch this video to see 6 tips for furnace troubleshooting:
Project step-by-step (13)
Step 1
Remove the Combustion Chamber Door
DIY furnace maintenance will save you from needing a new furnace. To fix your furnace, first flip the electrical power furnace 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.
Step 2
Inspect the Burner Flames
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. This furnace maintenance job should be done by a pro..
- Pro tip: While you’re inspecting the burner, Hiller cautions you to inspect the heat exchanger for cracks. If you see any, call for professional assessment, as they can allow carbon monoxide to seep into your home.
Step 3
Vacuum Out the Burner and Blower Cavities
Turn off the power switch again and shut off the gas by giving the valve one-quarter turn. Vacuum the furnace 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.
Step 4
Remove the Blower to Clean It
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.
Step 5
Vacuum and Brush the Blower Blades
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 balance.
Step 6
Change the Furnace Filter
Gabrielli advises: “You need to replace your air filter every so often (the period depends on your specific system, but every three months is typical) to make sure it has the right airflow and that your indoor air quality isn’t suffering.” 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.
Step 7
Blow Dust Off the Pilot
Blow dust off the pilot. Direct air to the exact spot by using a can of compressed air or, in a pinch, blowing through a drinking straw. A dirty pilot can cause the thermocouple to get a false reading that the pilot isn’t lit. Note that newer furnaces tend to have hot surface igniters or electronic igniters instead of pilots, so if you don’t see an open flame when the furnace is off, don’t worry. Your furnace is probably a more recent model.
Learn how to clean a furnace ignitor here.
Step 8
Clean the Flame Sensor
The flame sensor occasionally becomes coated with residue and will prevent your furnace from lighting. Cleaning it is a DIY furnace maintenance task, but you have to do it carefully. 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. Don’t apply too much pressure; flame sensors are fragile and easily damaged.
Step 9
Dust the Hot Surface Igniter Without Touching It
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.
Step 10
Inspect the Drive Belt
To repair your heating, the belts on belt-driven blowers need occasional adjustment or replacement. Inspect the drive belt for cracks or frayed areas. When you install the new belt, which is a DIY furnace job only for the more mechanically inclined, tension it so it deflects 1/2 to 3/4 in.
Step 11
Lubricate Bearings if Necessary
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!
Step 12
Adjust Dampers If Necessary
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.
If your furnace is blowing cold air, here’s our round-up of common conditions that cause furnaces to blow cold air, along with DIY fixes.
Step 13
Seal Leaky Air Ducts
Seal the leaky air ducts and return ducts that you can access 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. You may need to call a pro if you suspect leaky ducts buried behind a wall where you can’t see them.
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. If you’re looking for the best furnace to purchase, energy efficient brands might be the best bet.
About the Experts
- John Gabrielli is an expert in heating systems and HVAC repair. He is the owner of Air Temp Solutions in Sacramento CA.
- Mike Fisher is the General Manager of Energy Services at HomeServe USA.
- Jimmy Hiller is the President and CEO of Happy Hiller, a plumbing and HVAC company he founded in 1990.
