How to Clean a Furnace

A furnace is an expensive purchase, and if you’re trying to stretch a few more years of heating supply out of your unit, then it wouldn’t be a bad idea to perform a thorough cleaning. Of course, you can hire a professional to do it, but here we teach you how to clean a furnace on your own.

Tips for Cleaning a Furnace

Turn the furnace off and wait until it has cooled down.
If it is a gas furnace, make sure the pilot light is off.
With a wet cloth, wipe the exterior surfaces.
You’ll likely see dust all around the furnace, so go ahead and vacuum that.

Now it’s time to tackle the various components of the furnace.

How to Clean a Furnace Blower

before and after image of cleaning a furnace blower

If you want to clean the fan, then you need to start with a very important safety measure.

Disconnect the furnace from the power source (preferably at the circuit breaker).
Before you disconnect the blower, take a picture of how it is connected. That way, there is no confusion about how to reconnect it.
Disconnect the blower.
Remove the screws holding the blower housing in place and take it out.
Remove the circuit board bracket.
Using brushes, vacuums, and/or air compressors, clean the housing and fan as well as you can.
Clean the circuit board bracket. Be very careful not to damage the circuit board.
Reinstall the bracket on the housing.
Before you reinstall the housing, be sure to vacuum the furnace cavity where it belongs.
Reinstall the housing.
Reconnect the blower to the furnace and then to the power source.

How to Clean a Pilot

In this case, all you do is blow air onto it to remove the dust.

How to Clean a Flame Sensor

Remove the access cover on the furnace.
Locate the flame sensor.
Cut the power to the furnace.
Shut off the gas control valve.
Take out the flame sensor by removing the mounting screw.
Examine the part to see if it’s compromised, either by damage or dirtiness. If dirty, it just needs cleaning. If damaged, for example, the porcelain insulation is cracked, then it needs replacement. To clean it, use steel wool and lightly scrub it until you remove all traces of debris, rust, etc. Do the same for the electric igniter (if you have one).
Reinstall your new or cleaned flame sensor.
Turn on the gas valve and cut the power back on, and you’re back in business.

How to Clean the Heat Exchanger

removing panel showing how to clean a furnace

In an older unit, the heat exchanger is probably located within the draft hood. You have to remove the draft hood to access the heat exchanger. Remove the baffles from the tubes and brush around to loosen dirt, and then vacuum it.

Be Sure to Replace the Air Filter

Now that you’ve got a spotless furnace don’t forget to install a clean return air filter. This should be changed out every 1 to 3 months (monthly to stay on the safe side).

How to Clean Furnace Burners

If possible, leave the burners in place and just clean them with a long plastic and nylon brush. If you do need to take them out to properly clean them, try this helpful video.

Get New Furnace Parts at PlumbersStock

Now that you've cleaned up your furnace, you might be newly aware of parts that need replacing. We carry a huge inventory of HVAC parts like blowers and motors, furnace ignitors, blower wheels, etc. Did you know that you can find member pricing here on certain items (typically name brand, MAP priced items) if you log in? For industry professionals buying in bulk, please consider contacting us directly for extra special pricing and extra savings.