Heating IssuesHow to Clean a Furnace in 8 Easy Steps: Full Guide with Pictures

how to clean furnace in 8 easy steps


Jake Smith, Online Marketing Strategist
Technically Reviewed by Jake Smith, Online Marketing Strategist on December 26, 2023 | Written by Alpha Mechanical Editorial Contributors

Imagine you’re on your way home on the first chilly northern California night of the fall and winter season and you realize you forgot to do a furnace inspection before the cold weather hits. Although you might be nervous to turn on your thermostat for the first time each year, it is essential that you do so while the temperatures are still mild. You don’t want to find out your furnace needs to be replaced or is blowing dirty air and not working properly to be put on a waitlist for heating service or furnace replacement.

If you don’t know how to clean your gas furnace, scroll below to our step-by-step process or call an HVAC specialist to be on the safe side.

In this article we dive for natural gas furnace cleaning or propane furnace cleaning and examining (including a photo breaking down each step), however, most all tune-ups and maintenance on your furnace should be done by an HVAC professional.

Cleaning Furnace:
Why it is so important to do so?

Even though there is not a service-wide standard checklist to maintain furnaces, an HVAC technician may examine the following parts: heat exchanger, blow the motor, inducer motor, burners, and code history. It is important that you (as a homeowner) do not inspect or clean your own furnace igniters because they are extremely dangerous parts to misuse.
If you are in need of heating system repair, check out this page for further assistance.

There are several precautions you have to take before you begin cleaning your furnace:

  • Always turn off electrical power and fuel before you begin any work on your furnace
  • Keep tools and spare parts on hand including the correct screwdrivers to take off the door to the combustion chamber

Before getting started on your gas furnace cleaning, there are some essentials that you’ll need for the job:

  • Screwdrivers
  • Ratchet & Socket set
  • A vacuum cleaner with an upholstery brush attachment
  • Small stiff bristle brush
  • New return air filter
  • Emery cloth
  • Lubricating machine oil (needed for old 20-year furnaces)

I am considering alternate heat-source; What are my options?

Cleaning Furnace:
How to Clean a Furnace?

Step 1: Turn off power and cut off fuel supply to the furnace

Turn off power supply to furnace
cut off fuel supply

Turning the power off to the furnace should be a simple toggling of the switch or unplug. Depending on which fuel source you use (propane or gas) the valve should be near the furnace on the incoming gas pipe. Shut off the gas by turning the valve ¼ of the way.

Step 2: Clean Furnace Surface and Combustion Chamber

clean combustion chamber

To clean furnace burners, first remove the furnace access doors and remove the burner cover (if there is one) by loosening the screws.

Vacuum the burners and furnace base using the shop vac or the upholstery attachment to your vacuum making sure you reach every nook and cranny you can reach. Keep note of any indications of soot- this is a sign of poor combustion and will need some professional attention.

clean combustion chamber

To clean furnace burners, first remove the furnace access doors and remove the burner cover (if there is one) by loosening the screws.

Vacuum the burners and furnace base using the shop vac or the upholstery attachment to your vacuum making sure you reach every nook and cranny you can reach. Keep note of any indications of soot- this is a sign of poor combustion and will need some professional attention.

Step 3: Remove the blower

If the control panel blocks the blower, unscrew it to remove it using the socket and ratchet set.

Step 4: Clean the blower carefully

clean blower carefully

Staying cautious of the wiring and fan blades, vacuum out the furnace blower and clear any debris and dust with the small bristle brush. Poor cleaning of the blower could result in it becoming off-balance. Search the ductwork and any air ducts you have access to for any holes as well.

clean blower carefully

Staying cautious of the wiring and fan blades, vacuum out the furnace blower and clear any debris and dust with the small bristle brush. Poor cleaning of the blower could result in it becoming off-balance. Search the ductwork and any air ducts you have access to for any holes as well.

Step 5: Clean the flame sensor

clean flame sensor

Pull the furnace flame sensor (rod) down and out of its bracket, cleaning it delicately with an emery cloth and slide it back in when you’re finished. When the sensor is dirty, it can prevent the flame from igniting.

clean flame sensor

Pull the furnace flame sensor (rod) down and out of its bracket, cleaning it delicately with an emery cloth and slide it back in when you’re finished. When the sensor is dirty, it can prevent the flame from igniting.

Step 6: Lubricate fan motor

lubricate fan motor

Remove and clean the oil caps. Older furnaces (15-20 years old) have motor bearings and a shaft bearing. Apply 2-3 drops of lubricating oil, but be careful not to over-lubricate it. Finish by putting the oil caps back in place. This is an annual job.

New motor technology does not need to be lubricated. These motors self-lubricate because they have brushless technology. Please do not lubricate your motors because the oil will get into the electrical windings and burn the motor.

lubricate fan motor

Remove and clean the oil caps. Older furnaces (15-20 years old) have motor bearings and a shaft bearing. Apply 2-3 drops of lubricating oil, but be careful not to over-lubricate it. Finish by putting the oil caps back in place. This is an annual job.

New motor technology does not need to be lubricated. These motors self-lubricate because they have brushless technology. Please do not lubricate your motors because the oil will get into the electrical windings and burn the motor.

New motor technology does not need to be lubricated. These motors self-lubricate because they have brushless technology. Please do not lubricate your motors because the oil will get into the electrical windings and burn the motor.

Step 7: Replace the air filter

replace air filter

During the heating season, replace the filter quarterly. However, if you have pets in your home, it is necessary to replace the filter more frequently.

replace air filter

During the heating season, replace the filter quarterly. However, if you have pets in your home, it is necessary to replace the filter more frequently.

Step 8: Activate the burners

turn or burners

You can activate the furnace burners by turning the power and gas back on and then increasing the temperature on the thermostat. See that the burner flames are even and blue, if they are yellow this means they are dirty and need cleaning and adjusting done by an expert in the field. This is not a do it yourself job.

turn or burners

You can activate the furnace burners by turning the power and gas back on and then increasing the temperature on the thermostat. See that the burner flames are even and blue, if they are yellow this means they are dirty and need cleaning and adjusting done by an expert in the field. This is not a do it yourself job.

Furnace Cleaning: DIY or Professional

Cleaning, changing filters, and lubricating your furnace are fairly straightforward steps in ensuring your unit will work efficiently for the season. It may take you a few hours to become familiar with all of its parts but once you have done it a few times, a furnace cleaning should take 1-2 hours. Ensuring that your indoor air quality is at its top peak, changing the furnace filter quarterly is essential.

If you run into any of the situations below, it is time to consult a licensed HVAC technician:

  • Excessive soot: if you notice a build-up of soot has accumulated, this usually is because the burners need to be adjusted or the heat exchanger needs to be replaced. Call in an expert to diagnose and fix the issue.
  • Irregular flame: the pilot light flame should be blue; if yours is noticeably yellow or irregular, it can be an indication of dirty burners or a cracked heat exchanger. This also requires professional attention.

Today’s furnaces do not have pilot lights but spark ignition or hot surface igniters. This type of ignition does not need cleaning. Warning: hot surface ignitors should not be touched with bare hands, but handled properly. Oil from your skin will damage the material.

  • Short cycling: If your furnace starts running and then shuts down suddenly or unexpectedly it is known as short cycling. Short cycling is often caused by an out-of-order thermostat or an overheating exchanger. When your unit is short cycling, it could be a sign of cracked heat exchanger. Solve the problem, once again, by hiring an expert.

Some signs you need a new furnace:

  • Excessive soot in the burner compartment
  • Cracks or corrosion in the heat exchanger
  • If your energy bill is increasing but your usage of the furnace is staying the same

Want to learn why furnace won’t turn on?

Consider Alpha Mechanical your Trusted Partner

Alpha Mechanical has been serving Sacramento homeowners for over 20 years with its expertise. We service people in the Sacramento surrounding regions stretching from Lincoln neighborhoods down to Elk Grove. With quality service, fair pricing and an honest assessment our team is ready to help with any HVAC needs and desires you. Our team provides heating and cooling system repair and installation, furnace replacement services, indoor air quality services and much more with financing options for every customer as well as coupons and rebates. If you’re still unsure on how to service furnace or how often to clean furnace in your home, give us a call and we’ll be happy to help.

When our customers purchase new equipment through Alpha Mechanical, they are supplied with a 10 year warranty on the equipment and parts. In most cases, we provide a 1-2 year free maintenance service plan to clean the system with the purchase. Thereafter, we can discuss our service agreement plans, to maintain the longevity of the system.

However, if your heating and AC system is not maintained regularly, the warranty may be voided. Customers with existing systems can also purchase service membership plans (routine maintenance plans).

Final Thoughts

Before the crisp cool air settles in around the Sacramento area, make an appointment for your annual furnace inspection and tune-up. If you do not complete a maintenance appointment, your system can wear itself out faster and blow toxic carbon monoxide into your home or quit working altogether. Proper care for your furnace can ensure its lifespan and keep it running at a top-tier level.

Although your furnace system needs to be inspected once yearly, your furnace filter needs to be replaced more frequently (up to 4 times a year) and examined often if you have smokers or pets in the home. Some smart thermostats have the technology which provides internal reminders for when it is time to change out your filter based on how often you run your unit.Or, if you’ve got an aging unit and are considering upgrading with residential heat pump replacement in Sacramento, reach out to Alpha Mechanical to learn more.

Looking to extend the life of your HVAC Unit?

Frequently Asked Questions

Frequently Asked Questions

How to clean a furnace?

Turn off the power and cut off the fuel supply to the furnace, clean furnace surfaces and combustion chamber, remove the blower, clean the blower carefully, clean the flame sensor, lubricate the oil caps, replace the air filter, and activate the burners once you’re done.

How do I clean furnace burners?

First, remove the furnace access door and burner covers, vacuum the burners using a shop vac or wand attachment on your vacuum, reaching every part of it you can. Reinstall covers when completely finished. For any further cleaning, we advise you to call a professional.

How do I know how often to clean the furnace?

Furnace cleaning should be done once a year, preferably before the cold weather kicks in. Furnace filters should be replaced quarterly.

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