A gas furnace works hard, and it needs regular cleaning and maintenance to provide reliable heating for many years to come. A well maintained and clean gas furnace will help you to reduce the chances of an emergency repair, and it could extend the useful lifespan of your equipment. As our heating season is coming to an end, it’s the perfect time to clean your gas furnace and get it ready for later in the year when the colder weather returns. In this article, we will show you the ten steps to cleaning your gas furnace.

Gathering Tools and Supplies

Cleaning your gas furnace should be an annual event, and it makes sense to schedule the process at a time when you don’t need heating. Spring or early fall are ideal times, but many homeowners forget about it until it’s too late. So, if you clean the gas furnace earlier, it will be ready to use later in the year. The first thing that you need is some essential tools and supplies, including a set of screwdrivers, a ratchet and socket set, a small stiff brush, an emery cloth, a shop vac, a straw, a clean rag, a fresh furnace filter, and some lightweight machine oil. Once you have your tools and supplies follow these steps carefully and if you’re not confident working on you gas furnace contact a local HVAC specialist for expert help.

Step 1: Shut Off Gas and Power

The power needs to be turned off at the breaker box to make sure it’s safe to work on the gas furnace. Locate the breaker box electrical power switch and place it in the “Off” position. Then locate the gas valve and shut it off with a ¼ turn, and you’re ready to start cleaning.

Step 2: Cleaning Exterior Surface

Now we can begin cleaning, and the first task is to clean the exterior surfaces to remove the accumulated dust, dirt, and grime deposits. Take the clean rag, wet it, and wring it out, so it’s damp and wipe down the exterior of the gas furnace. Then remove the gas furnace access door by lifting it slightly and pulling it out. Remove the gas burner cover (some furnaces don’t have one) and use the shop vac to vacuum the burners and the base of the furnace. If you’re using a regular vac, you may need to try a few different attachments before you find the right one for the job. Get as far into the back of the furnace as you can and vacuum inside the blower door and compartment. During this cleaning process, keep an eye out for any soot deposits, which could indicate a poor level of combustion. If you do find any soot contact an HVAC specialist and schedule some maintenance to fix the problem.

Step 3: Remove and Clean the Blower Unit

Locate the control panel and unscrew it if it’s in the way of the blower unit. Then take your socket and ratchet set and carefully remove the bolts that secure the blower unit in place. Keep the bolts in a safe place and remove the blower unit gently to avoid damage. Take care to avoid disturbing the counterweights and wiring on and around the fan blades. Use the small stiff brush to remove tough deposits of dirt and the vacuum for general cleaning. It’s important to clean the blower unit evenly, leaving one side dirty could throw the blower out of balance. Once the blower is clean, replace it by following the instructions above in reverse.

Step 4: Cleaning the Igniter

Now it’s time to clean the hot surface igniter or pilot using the drinking straw. Simply blow any dust deposits away gently using your breath until the area is clean and clear. If you have a hot surface igniter be very careful; don’t touch this part because it’s fragile and easily broken. Once you’re finished, replace the furnace doors to keep these parts safe.

Step 5: Cleaning the Flame Sensor

The flame sensor can be pulled down and out of the bracket gently for cleaning. Take the emery cloth and gently clean the surface of the flame sensor. Then slide the part back into place, and you’re ready to move on with your cleaning.

Step 6: Inspecting the Drive Belt

The blower unit has a belt that can fray or crack over time, much like the fan belt in a car. When the blower belt degrades in this way, it will gradually lose tension, and the performance will suffer. A new blower belt can cost as little as $10, so it’s a good idea to simply replace it regularly. The new or existing belt needs to have enough tension to deflect between ½” up to ¾”.

Step 7: Lubrication

Locate, remove, and clean the oil caps, then use the light machine oil to lubricate the blower motor unit and the shaft bearing. Take care to use very little oil; you only need to apply 2 or 3 drops of oil to keep everything running smoothly.

Step 8: Replacing the Air Filter

The furnace filter should be changed every three months to protect your HVAC system from damage. The process is detailed in the owner’s manual along with the air filter recommendations for your system. Avoid the temptation to install high efficiency filter without checking if they are compatible first because this can cause considerable strain on your HVAC equipment.

Step 9: Check the Burners 

Restore the power supply and turn the gas back on, they activate the burners by adjusting your thermostat. Take a look at the burner flames; they should have a blue color and be even and steady. If the flame is yellow, it means that the burners are dirty, and cleaning or adjusting them is a job for an HVAC specialist. 

Step 10: Adjusting Dampers

Many homes have heating ducts that also act as air conditioning ducts. It’s necessary to adjust the dampers to match your seasonal setting for the best performance.

General Advice

If you’re not confident working with HVAC equipment, it’s a better idea to contact a local HVAC professional for an annual service, which includes cleaning the furnace. If you decide to clean the gas furnace yourself, always check the owner’s manual for advice and take pictures at each step to remind you how things fit together.