Dirt is the silent killer of your furnace. It wastes fuel. It slashes efficiency. In extreme cases, it makes the unit overheat. You can ignore the rest of the system, but if you don’t clean these three components, you’re fighting a losing battle: the filter system, the blower, and the motor.
Why a Dirty Filter Ruins Your Heating System
The filter is the first line of defense. Replace or clean it at the start of the heating season. Then check it once a month during heavy use.
Here is the test. Pull the filter out. Hold it up to a light. Can you see the light through the mesh? If it looks clogged, toss it. Do not worry about how many weeks it has been in there. A dirty filter is a dirty filter. Replace it with the exact same type and size.
Disposable filters are fiber mesh in a cardboard frame. The size is printed on the edge. Look for the arrow. That arrow shows airflow direction. Air moves from the return duct toward the blower. So the arrow must point away from the return duct and toward the blower. Got it backwards? You’re blocking your own heat.
Permanent filters need a different touch. Spray them with a special filter-coating chemical found at any hardware store. Follow the manufacturer’s instructions attached to the furnace housing. Don’t guess. Read the label.
Step-by-Step: How to Replace and Clean Your Furnace Filter
Ready to get your hands dirty? Here is how you do it without stripping bolts or bending metal.
- Find the metal panel on the front of the furnace. It sits below the return-air duct, between the duct and the blower system. It might say “filter” on it. Or it might just look like a lid on a boxy part of the housing.
- Remove the panel. Slip it off its hooks. Unscrew it if necessary. Some units have exposed filters. Just slide them up and out of the U-shaped tracks.
- Inspect the filter. Clean it if it’s permanent. Replace it if it’s disposable.
- Clean the blower assembly. This includes the belts, pulleys, and motor housing.
Cleaning the Blower and Squirrel-Cage Fan
This part is critical if you have a squirrel-cage fan. Those openings clog with dirt fast.
To clean the blower, remove the panel you took off in step two. Or remove the front panel if that’s where the access is. It’s usually held by slip-fit hooks or retaining screws.
Once inside, slide out the fan unit. It sits on a track held by screws. Don’t force it. Slide it out gently. Clean the dirt from the blower wheel and the housing. Put it back. Screw it down.
A clean furnace runs cooler. A cooler furnace lasts longer.
Troubleshooting Gas Furnaces Next
You’ve cleaned the filter. You’ve wiped down the blower. The air should move better now. But what if it still won’t start? What if it clicks but no flame?
That’s a different beast. We’ll look at troubleshooting a gas furnace next. Until then, keep that filter clean.
