Need More Help? Use the Form Below or Call 1-888-559-6352

The email address and phone number are good ways to reach me.

Why is my furnace making noise?

Mar 05, 2019

The blue and yellow Cropp Metcalfe Services logo with bold lettering.

It’s not uncommon for homeowners to hear strange noises coming from their heating systems at one time or another throughout the winter, especially in older homes. It is important, however, for homeowners to pay attention to the types of noises their furnaces are making.

Is your furnace making a light whistling sound, or did you hear a loud crash? These noises have very different meanings and can indicate serious issues with your furnace.

Let’s explore the types of sounds furnaces make and what these noises mean for homeowners.

Read more: How’s Your Furnace Doing So Far?

Loud Boom

Sometimes your furnace will make a loud “boom” sound when you first turn the heat on for the season. This is usually due to dirty burners causing a delayed ignition, and is something your HVAC technician will address during your regular fall HVAC inspection. What’s not normal, however, is a sudden, seemingly inexplicable banging sound coming from your heating system in the middle of winter.

One explanation for this startling sound is expanding and contracting ductwork. If you have a central HVAC system, you’re probably used to hearing your ducts warp from time to time during the heating season. Some relatively easy solutions for noisy ducts include sealing and insulating ducts or replacing air filters.

Unfortunately, noisy ducts aren’t the only potential cause of this sound. A loud, sudden boom could indicate a gas buildup in your system, which can ultimately lead to dangerous and expensive damage, like a cracked heat exchanger.

If you’re unsure why your furnace is making noise, turn off the system and contact an HVAC professional immediately.


After years of consistent use, it’s possible that a panel or screw in your heating until has come loose, resulting in a rattling sound. First, be sure to cut off the power to your furnace before attempting to fix the problem. Once the power is turned off from the source, you can inspect the furnace and tighten up any loose panels or screws.

If you don’t find any loose panels or screws, there’s a chance your heat exchanger is faulty. A damaged heat exchanger can result in dangerous gas leaks, putting you and your family at risk of carbon monoxide poisoning. It’s important to call an HVAC service ASAP if you’re unable to fix the rattling sound on your own.

Metallic Scraping

Screeching, metal-on-metal sounds are not only unpleasant, but can also indicate a serious problem with your furnace’s blower wheel. Damage to your furnace’s blower wheel could be caused by:

  • Loose blower fan. It’s possible that the blower fan has slipped out of place, causing the blades to hit the casing. This is usually an easy repair as long as the blower fan and wheel haven’t been damaged in the process.
  • Broken fan blades. If your blower’s fan blades are seriously damaged or broken, your blower fan will likely need to be replaced.

There’s also a small chance that the part that connects the blower assembly and the motor has broken, leading the entire assembly to detach and fall out of place. A professional will need to inspect your furnace to properly diagnose this issue.

While you and your family are in no immediate danger by running the heat with a damaged blower assembly, it’s best to turn off the furnace until a licensed technician can inspect the unit. Running your furnace with a broken blower wheel could result in more costly damages down the road.

High-Pitched Whistling

Luckily, squeaking or whistling sounds are the least concerning of furnace noises. Common causes of high-pitched furnace noises include:

  • Loose or damaged blower belt. An HVAC professional can take care of this issue with relative ease.
  • Dry shaft bearings. Moving parts are typically lubricated during your fall HVAC inspection.
  • Blower motor malfunction. It’s possible that your furnace’s blower motor may need replacement. You’ll need to contact a heating technician to determine if the motor is causing the whistling noise.

Furnace Troubleshooting with CroppMetcalfe

Many of the strange sounds coming from your furnace can be prevented with annual HVAC tune-ups, however, unexpected problems can arise and should never be ignored.

Avoid expensive repairs and dangerous gas leaks by scheduling regular furnace maintenance and contacting the 5-Star Technicians at CroppMetcalfe if your furnace is making noise. We can diagnose and address a variety of furnace-related issue to ensure you and your family are safe throughout the winter.


What Our Customers Say...

"I've been a CroppMetcalfe customer for 9 years and you have always provided outstanding service. I just had my semi-annual maintenance done, and I wanted to thank George for the truly outstanding service, professionalism, and excellent advice. He is definitely one of the best 5-Star Technicians I've had! Thank you CroppMetcalfe!"

Bill H