Why Is My Furnace Making a Banging, Rattling, or Grinding Noise?

When it’s working normally, your furnace shouldn’t make much noise. That means that if your furnace is making noise while running, such as loud bangs, rattling, or grinding, it’s a sign of a problem with the system. In this guide, we’re going over the noises a furnace might make, what they may mean, and when it’s time to call a pro.

What Do Different Furnace Noises Usually Mean?

If your furnace is making a loud noise while running, you shouldn’t ignore the issue. Loud noises indicate a problem with one or more internal components of the system. These issues don’t fix themselves, so we advise contacting a furnace noise repair pro if you notice them.

Why Does My Furnace Make a Loud Bang When It Turns On?

One sign that your heater needs repair is hearing a loud bang. There are two common causes for these sounds.

Delayed ignition

The most likely cause of your gas furnace banging when it turns on is delayed ignition. This means that natural gas is building up in the combustion chamber before it gets ignited, which essentially causes a small (but very loud) explosion inside the furnace. Obviously, this is bad for your system. Delayed furnace ignition is often caused by dirty burners.

Expanding or contracting ductwork

Another possible cause of your furnace making a banging noise is issues with the ductwork. When your ducts get exposed to heat after being cold for a while, the metal expands, leading to banging noises in the ducts. You’ll know this is the issue if it takes a few minutes of running the furnace for the noise to start.

Why Is My Furnace Rattling While It Runs?

Rattling is another unsettling sound to hear from your unit. Furnace rattling noises usually mean a component is loose and getting vibrated around. This can sometimes be a simple loose screw or access door, which requires repair but isn’t too serious an issue.

When is rattling more serious?

You might be hearing a furnace blower motor noise, which happens when debris builds up on the motor (or a screw comes loose), causing it to become imbalanced and rattle loudly while it spins. Rattling sounds might also come from a failing inducer motor. You’ll need a pro to inspect the system and eliminate the rattling sound.

Why Is My Furnace Making a Grinding or Scraping Noise?

If your furnace is making a scraping noise or sounds like metal grinding on metal, it’s a sign of a serious issue. Furnace grinding noises mean a component is loose or that there’s been a mechanical failure. The problem could be:

• Loose or broken blower wheel.
• Failed motor bearings.
• Malfunctioning motor mount.
• Debris and dust buildup in the system.

Why you shouldn't ignore metal-on-metal sounds

Continuing to run a system that’s making a metallic scraping noise will severely damage it. Because these noises indicate a component being damaged or out of place, you should shut the system off and have it inspected by a pro as soon as you notice them.

When Is a Furnace Noise Normal?

We’ve looked at what furnace noises are dangerous, but what about ones that are normal? There are a few sounds you’ll hear during normal furnace operation:

• Click: You’ll hear a faint click from the system when it starts up, indicating that the ignition system has fired up.
• Low hum: A quiet humming sound is your blower motor operating.
• Whoosh: A soft whooshing sound is caused by warm air moving through vents.
• Quiet popping: Low pops are caused by minor contractions and expansions in the metal of your ductwork.

Which Furnace Noises Mean You Should Turn the System Off?

If you hear the following noises, it’s a sign of a serious issue. To prevent damage to the system or possibly a safety issue (such as a dangerous gas leak), shut the system off and call a heating repair technician if you hear the following noises:

• Loud banging or booming.
• Metal-on-metal grinding, screeching, or scraping.
• Hissing, especially if accompanied by a sulphuric, rotten-eggs smell.
• Electrical buzzing.

What Can You Check Before Calling for Furnace Repair?

One of the main things to check before calling for professional heating services is your air filter. Most filters need to be replaced every 30 to 90 days. You can also double-check your thermostat to make sure it’s on and set correctly. Also, be sure to confirm that the heater’s circuit breaker is flipped on.

For any other diagnostic or repair tasks, you should work with a trained HVAC professional. Attempting DIY repairs puts you at risk of further system damage or a health and safety hazard.

Can a Dirty Air Filter Make a Furnace Noisy?

Dirty air filters prevent your heater from getting the air it needs to run, which can definitely lead to loud noises during operation. The blower motor is under greater strain with lower airflow, which can cause it to make more noise during operation. This is why changing the air filter is usually the first troubleshooting step for any furnace issue.

Does a Noisy Furnace Need Repair or Replacement?

If your furnace is less than ten to 15 years old, generally functions well, and has only recently started making a noise, you should be able to repair it with the help of a professional. If your system is older than that, facing multiple issues, or in constant need of repair, it will probably be more cost-effective in the long term to replace it.

Why Do Furnace Noises Often Show Up at the Start of Heating Season?

You’re most likely to notice loud furnace noises at the start of the heating season. This is because your system has sat inactive for several months, which allows lubricant to dry out and dust to settle on internal components. This is why HVAC experts always recommend having your system proactively maintained in the fall, right before you’ll be using the system daily.

When Should You Call a Canyon Air About a Furnace Noise?

If you have any concerns about your furnace, play it safe and contact the pros at Canyon Air. We can quickly diagnose and repair the issue. If you need significant repairs or a new system, we can help make it more affordable with flexible financing and special offers, so you can ensure a cozy heating season without breaking the bank.

Enjoy a Quiet, Quality Furnace

If you’re tired of wondering what that loud noise from your heater is, we’re here to help. Contact our team today to schedule a furnace service appointment and get your unit ready to run.