Haunted House or Just Poor Maintenance? 7 Spooky HVAC Noises Explained

It’s late October, the wind is howling across the prairie, and your house is making… that noise again. Before you call a priest, let’s make sure you don’t just need a new filter. Here’s a fun (but actually useful) guide to the 7 spooky HVAC noises Des Moines–area homeowners hear every fall—and what to do about them.

Whether you’re in Ankeny, West Des Moines, Urbandale, Johnston, Waukee, Altoona, or right in the city, these tips will help you separate haunted from needs maintenance—and know when to call Obsidian Heating & Cooling.

1) The “Basement Banshee” (High-Pitched Screech or Whine)

What it sounds like: A squeal, screech, or violin-from-a-horror-movie tone when the furnace starts.

Likely culprit: A worn blower motor bearing, misaligned belt (on older units), or a failing inducer motor. If the noise rises and falls with the blower speed, it’s often the blower assembly.

Try this first:

• Turn the system off at the thermostat and check your filter. A clogged filter forces the blower to work harder and can amplify motor whine.

• If the noise persists when the blower spins up, it’s time for a pro to check bearings and balance.

When to call Obsidian: Screeching typically won’t resolve on its own—and continued operation can accelerate wear.

2) The “Attic Apparition” (Rattles and Tinkles)

What it sounds like: A rapid rattle or tinkle, especially during startup or when the blower kicks to a higher speed.

Likely culprit: Loose panels, unsecured duct screws, or a vibrating vent grille. Metal expands and contracts as it warms and cools, and those little gaps get chatty.

Try this first:

• Inspect the furnace panel screws and tighten them.

• Look for register covers that shake when air flows; snug up loose screws.

• Make sure nothing is sitting on top of the furnace (it happens!).

When to call Obsidian: If the rattle is deep inside the unit or grew suddenly after a repair, you may have a loose blower wheel or inducer housing issue.

3) The “Coffin Lid” (Boom/Thump at Ignition)

What it sounds like: A single boom right as the furnace fires, like a door slamming in the distance.

Likely culprit: Delayed ignition—gas builds up for a moment before lighting. Common causes include a dirty burner, weak igniter, or misaligned flame sensor. Another possibility is oil-canning ducts that flex loudly as pressure changes.

Safety note: Repeated booming can damage the heat exchanger and is not something to ignore.

Try this first:

• Replace the filter and make sure all supply and return vents are open.

• If the boom persists, shut the system down and call a pro.

When to call Obsidian: Immediately if the boom is frequent or loud. We’ll inspect ignition, burners, and gas pressure for safe, smooth starts.

4) The “Chain-Dragging Phantom” (Grinding or Metal-on-Metal)

What it sounds like: A low, ominous grind when the blower runs.

Likely culprit: Blower wheel scraping the housing or failing motor bearings. Sometimes a small foreign object (screw, drywall scrap) gets inside the blower compartment.

Try this first:

• Turn the system off. Grinding can quickly turn a small repair into a big one.

• Check for obvious obstructions at the blower intake.

When to call Obsidian: ASAP. We’ll realign the wheel, replace bearings/motor if needed, and ensure the housing isn’t damaged.

5) The “Poltergust” (Whoosh, Whistle, or Wind Tunnel)

What it sounds like: A constant whoosh or whistling at certain registers or when the door to a room is closed.

Likely culprit: High static pressure (restricted airflow). Causes include undersized returns, closed or blocked vents, or a high-MERV filter that’s too restrictive for your system.

Try this first:

• Open every supply and return vent fully—even in rooms you rarely use.

• Swap to a clean filter appropriate for your system’s airflow (your filter cabinet and blower size matter).

• Move furniture, rugs, or drapes that may be blocking registers.

When to call Obsidian: If whistling continues, we’ll test static pressure and recommend airflow fixes—return additions, filter cabinet upgrades, or mild duct changes. Your furnace will run quieter, last longer, and heat more evenly.

6) The “Dry Bones Chorus” (Clanks, Clinks, and Pipe Knocks)

What it sounds like: Metallic clanks or knocking that seem to come from the ducts when the system starts or stops.

Likely culprit: Thermal expansion—sheet metal expanding/contracting as it heats and cools. Poorly supported duct runs can “pop.” Hot air hitting colder metal amplifies the effect.

Try this first:

• Note which ducts are noisiest and ensure they’re properly supported.

• Check that dampers are fully open; half-open blades can knock as air hits them.

When to call Obsidian: If the noise is extreme or new, we’ll inspect for ductwork oil-canning, loose takeoffs, or poorly pitched runs that need minor rework.

7) The “Whispering Wraith” (Hiss Around the Furnace)

What it sounds like: A subtle hiss near the unit or certain joints.

Likely culprit: Very often air leaks in the return plenum or around the filter door, pulling unfiltered, dusty air into the system (which can dirty your blower and coil). Much more rarely, it could be a gas leak—gas leaks usually have a sulfur/rotten egg smell and demand immediate action.

Try this first:

• Replace the filter and make sure the filter door is sealed.

• Look for obvious gaps at seams; a pro-grade mastic/sealant can help.

When to call Obsidian: If you suspect gas, shut it down and call immediately. If it’s airflow hiss, we’ll seal returns and improve filtration so your system breathes right.

Bonus: “What’s that funky smell?”

We hear this every fall. When the heat first kicks on, a dusty smell is normal for a short while—it’s just burning off summer dust. Electrical, burning plastic, or smoky odors are not. We’ll cover smells in detail soon. “What’s that funky smell? That’s for a different blog post.”

Quick DIY Checklist Before You Panic

• Replace the air filter (1–3 months is the rule of thumb, more often if you have pets or renovations).

• Make sure all vents and returns are fully open and unblocked.

• Check thermostat batteries and settings.

• If the system is making scary metal sounds, power it down and call a pro.

When to Call Obsidian Heating & Cooling

If your furnace is sounding like a haunted house, we’ll bring it back to friendly-boo status. Our certified techs serve Ankeny, Des Moines, West Des Moines, Urbandale, Johnston, Waukee, Altoona, and nearby communities. We’ll diagnose the noise, fix the root cause, and make sure your system is safe, efficient, and ready for November.

Don’t wait for the jump scare. Call Obsidian Heating & Cooling or book online for a pre-winter tune-up or furnace repair today.