4 Common Causes Of A Noisy Furnace And How To Fix Them

Your furnace is an important part of your home and with regular maintenance it will serve you well for decades. Proper maintenance of your furnace includes noticing strange noises that come from it. These noises indicate that your furnace is developing problems or has already developed problems. Never ignore these noises.

Modern furnaces are more efficient than ever, but this efficiency comes with a lot of technical complications. Today’s furnace technicians are highly trained specialists. 

There are different causes of a noisy furnace that should be looked into as soon as you hear them. Fortunately, these noises can be too loud to ignore, which means you’ll correct them as soon as possible. For your reference, here are the common causes of a noisy furnace and how to fix them. Before you check any of these things, look at the state of your furnace filter. If it’s not squeaky clean, clean or replace it. Furnace filters are more sophisticated than they seem, and there’s even an interest story about how these filters are made. Did you know that some companies made the filter media itself, while others specialize in the cardboard frames that get applied around the filter media? I was surprised by this level of specialization, as you can see on the paperboard filter frame website here

Damaged Blower Belt

The blower belt connects the blower motor and fan together so warm air flows through your ducts. If you hear a high-pitched squeal that lasts for a few minutes when the furnace turns on but stops, your blower belt is likely to lose or be damaged. If you hear grinding noise when your furnace turns on, it could mean that your blower bearings are failing. 

A damaged or loose blower belt can be fixed in the following ways: 

  • Tighten or loosen the belt, changing the tension of the belt. 
  • Contact a professional to replace the damaged blower belt. 

If you want to learn how to adjust the blower belt to reduce the squealing, you can check resources such as the Technical Hot & Cold’s HVAC repair blog, among other resources.

A Dirty Burner

A noisy furnace is often a result of a dirty burner. This is often caused by the build-up of carbon and combustion deposits. The problem is that the burner develops a film along with creosote deposits, leading to rusting and clogging. When the burner is clogged up, it cannot get sufficient air and causes the fuel to burn improperly. This causes the furnace to make a loud popping noise or even cause it to blow out blue flames. 

Here’s how you can fix this problem: 

  • Annual inspection and cleaning of the burner. 
  • Replacement of damage or excessively worn burner may be required.  

One furnace sound that’s not an issue is a “thud”, most noticeable after the furnace shuts off. This is the sound of metal air ducts expanding and contracting. This isn’t an issue and  doesn’t indicate any damage to the furnace, or dirt in the burner.

Faulty Heat Exchanger

The heat exchanger is the part of your furnace that transfers heat from the burning gases to the warm air delivered to your home. Exhaust gases and household must never mix. If there are cracks in the heat exchanger, it may make a rattling sound when in use. This could also be a loose panel or a loose screw, but if tightening the panel doesn’t do the trick, the problem could be more severe. Cracks are a serious problem that can lead to carbon monoxide entering your home. A failed heat exchanger usually means the furnace needs to be replace. 

Some of the ways of fixing a heat exchanger include the following: 

  • Try to tighten any loose nut, screw, or panel first to see if the rattling sound stops. 
  • Call a professional to assess the severity of the crack to determine if it will be repaired or replaced. 

Other indications of a faulty heat exchanger include soot from inside the furnace, unpleasant odor, and water on the floor around the furnace. 

Out of Balance Blower Wheel

The blower wheel is the fan that pushes air through your heating system. If the blower wheel comes loose, it can cause a rattling noise in your furnace, mainly as it spins. This can also happen if the blower wheel has become bent or worn over time. An out-of-balance blower wheel will cause a grinding and scraping sound. 

Here’s how you can fix it: 

  • Remove the screws that hold the blower, then replace the blower or rebalance it. The sound should have gone after turning it on. 
  • Call a professional contractor to realign the blower if the sound is still there. 

You should note that the blower wheel will occasionally loosen itself, so it’s essential to conduct regular maintenance

Bottom Line 

A loud furnace can be an annoyance, but don’t just live with it. It’s important to pay attention and look into the causes a noisy furnace. Sometimes you can fix the issue yourself, but for most sources of noise, probably not. That’s what professionals are for.