Save a Repair Bill This Fall with This 13-Step Furnace Maintenance Guide!

It is important to have your furnace inspected regularly, but a professional inspection, furnace service, and repair can run you $100 or more depending on where you live and the time of year. Fortunately, you can easily save on this process by conducting it yourself.  Here’s how.

1. Remove the Combustion Chamber Door

Before performing any maintenance, make sure to switch off the electrical power and the fuel supply. You can find the red power switchplate near the burner itself or at the top of the cellar stairs. The fuel shutoff valve should be near the oil tank or on the incoming gas pipe. In case of a future leak or fire, make sure you know the location of both.

After making sure that the power is switched off, remove the combustion chamber door by lifting and pulling it out. Then remove the burner cover, which is normally held in place by two screws.

2. Inspect the Burner Flames

Power the furnace back on, turn up your thermostat to activate the burners and look at the burner flames. What color are they? If they’re fairly even and blue, you’re good to go. If they’re yellow, your burner is dirty and you should call a professional to have them cleaned. Never attempt to adjust the burners yourself, and be careful not to breathe on the flames while inspecting them, as the oxygen in your breath can make them turn yellow.

3. Vacuum Out the Burner and Blower Cavities

If your burners are clean, switch the power back off and give the gas valve one quarter turn to shut it off. Then, everywhere you see dust, vacuum out the burners and the furnace base. Use a flashlight to keep an eye out for signs of soot, as this can be a sign of poor combustion. Next, remove the blower door and vacuum out the blower compartment.

4. Remove the Blower to Clean It

If there is a control panel in front of the blower, loosen the two screws holding it in place and let it hang. Then, remove the two bolts holding the blower in place with a 7/16 inch socket and ratchet. Lift the blower out.

5. Vacuum and Brush the Blower Blades

Carefully, using a vacuum and a small brush, clean the blower blades. Try not to disturb the wiring or the counterweights. Don’t try to clean the blower at all if you can’t do it thoroughly, as this could throw it off balance.

6. Change the Furnace Filter

You should change the furnace filter every one to three months, but you should never let it go for more than a year without being switched out. All of the air you breathe has to pass through this filter. A cheap fiberglass filter should do but you can also use a more expensive, high-efficiency filter if you prefer. However, these high-efficiency filters can backfire, restricting the airflow and making the furnace-less efficient.

7. Blow Dust Off the Pilot

Blow through a drinking straw to get the dust off the pilot. If the pilot is dirty, it can cause the flames sensor to think that the pilot isn’t lit when it is. Certain newer furnaces might have hot surface igniters instead of pilots and electronic igniters.

8. Clean the Flame Sensor

If the flame sensor is coated with residue, it can prevent your furnace from lighting. Pull it down out of its bracket and clean it lightly with fine emery cloth before replacing it.

9. Dust the Hot Surface Igniter Without Touching It

If your furnace has a hot surface igniter, clean the dust off by blowing through a straw. Do not touch the igniter because it can break very easily.

10. Inspect the Drive Belt

Inspect the drive belt for cracks or frayed areas. If you need to replace the drive belt, you can get a new one for around $5. After installation, tension the new belt so it deflects ½ to ¾ inches.

11. Lubricate Bearings if Necessary

If your furnace is older, it probably has two motor bearings and two blower shaft bearings. Find the oil caps, clean around them, and remove them. Being careful not to over-lubricate, apply two to three drops of lightweight machine oil before replacing the caps.

12. Adjust Dampers if Necessary

If your furnace heating ducts double as air conditioning ducts, they probably contain dampers that need to be adjusted seasonally. These seasonal settings should be marked. If you live in a two-story home, chances are you will have separate supply trunks for both the upstairs and downstairs.

13. Seal Leaky Air Ducts

Use special metal tape for high-temperature silicone to seal leaky ducts, paying special attention to return air ducts. Conduct a back-drafting test by adjusting the thermostat to activate the burners and holding a smoking stick of incense beside the draft hood to see where the smoke goes. If it is drawn into the hood, you’re good to go. Additionally, while your furnace and water heater are still cool, inspect the exhaust vent pipes for white powdery residue, which can indicate corrosion. If you find any problems, they should be addressed by a professional.