Buzz, Rattle, Bang-Why Is My Furnace Making Weird Sounds?

South End Plumbing, Heating, & Air Expert Tips

Why Is My Furnace Making Weird Sounds

Buzz, Rattle, Bang-Why is My Furnace Making Weird Sounds?

So just what is that noise coming from your heater? Don’t worry, we’ll assist you fix the sound you’re hearing. We should let you know that any noises are not normal and are typically a sign of an issue that a specialist will need to fix.

Let’s go over some of the main categories of sounds:

  • Banging
  • Rattling
  • High-pitched squeal or whistling
  • Humming &  buzzing
  • Constant Clicking

Gas Igniter Failing
Gas Igniter Failing

Clicking Sounds

If your heating system is making a clicking sound, it normally indicates there’s a concern with the ignition system.

The ignition system is accountable for creating combustion, which is how your heating system develops heat. If the furnace can’t spark for some reason, then you may hear a clicking noise as the igniter has a hard time lighting.

Common ignition problems that trigger a clicking noise include:

  • The burners are dirty
  • No gas is reaching the system due to a faulty ignition board or a bad valve
  • The pilot light is snuffed out or the thermocouple is broken (only applicable to older heaters)
  • The flame sensing unit is broken

Besides the ignition problems above, a damaged fan motor can also cause a clicking noise if the bearings are loose.

Solution: Have an expert examine your furnace ignition system and fan motor.

Banging Sounds

You could have either one of these faulty conditions; Delayed Gas Ignition or Expanding/Contracting Air Ducts

Faulty Condition 1: Delayed gas ignition issue
If you hear the banging noise when your furnace initially switches on, then your furnace may not be lighting right now like it’s supposed to.

When a furnace does not fire up right away, gas develops in the combustion chamber. After the heating system finally fires up, all of the built-up gas creates a small surge, which can damage your heating system.

The following issues trigger postponed ignition:

  • Dirty or misaligned burners.
  • Low gas supply.
  • Broken pilot burner (with older furnaces).
  • Too much air mixed with gas.

Solution: Contact a professional to examine your heater ignition system and fix any problems.

Faulty Condition 2: Expanding/warping ductwork
If you hear intermittent banging sounds while your furnace is running, it could indicate you have to expand or contract ducts. (You’ll likely hear these sounds throughout your home, not always by the real heater itself).

When hot air gets pushed through the supply side of your home’s ductwork, it produces positive pressure which can trigger the ducts to broaden. In addition, when your heater pulls in cold air to be heated on the return side, it develops negative pressure which can cause the ducts to contract.

Since ducts are frequently made from sheet metal, it’s normal for ducts to make sounds from time to time as they broaden and contract. However, if the banging noises are distractingly loud or regular, it might suggest there’s a problem.

Issues that cause extra loud ducts include:

  • Dirty air filter.
  • Closed or blocked vents.
  • Undersized or filthy ductwork.Solution: Contact an expert to check your ductwork. They can see what is triggering the loud banging noise issue and recommend an option.

Whistling & Squeals

A high-pitched screech originating from your heating system is usually the outcome of a concern with the blower.

The blower in your heating system is powered by a motor, which has bearings that can wear because of age or overheating. Overheating is typically brought on by dirt buildup or a bad capacitor.

On the other hand, a high-pitched whistling sound is typically the result of a low airflow issue. Low airflow indicates that the blower is having a hard time drawing in enough air to be heated.

Common reasons for low air flow consist of:

  • An unclean air filter
  • Closed or blocked air vents
  • Dirty or damaged ducts

Solution: If you hear a high-pitched whistling noise, try altering your air filter and opening all vents to see if that fixes the problem. If that doesn’t work or you hear the squealing sound, call an expert for more assistance.

Buzzing & Humming

A dull hum is typical while your furnace is running. If you hear a loud humming or buzzing sound coming from your heater, it typically means your furnace has an electrical problem.

The most common electrical issues that trigger a humming or buzzing sound consist of:

  • Bad inducer motor
  • An aging or unlubricated blower motor
  • A faulty transformer
  • A failing blower motor capacitor

What to do: Contact an expert to check the electrical components of your heating system to identify the problem and fix it.

Heat Exchanger – Furnace Making Weird Sounds
Heat Exchanger – Furnace Making Weird Sounds


A rattling noise coming from your heating system indicates 1 of 2 faults:

  • A loose part
  • A cracked heat exchanger

Fault 1: Your heater has a loose part.
A furnace is an intricate piece of mechanical device, which indicates it has a lot of moving parts. Sometimes parts can end up being loose in time or because they were not tightened properly.

Common loose parts that make a rattling sound consist of:

  • Bearings in the blower motor
  • Panels around the heater
  • Connections in the ductwork
  • Worn blower motor fan belt (only suitable for older heating systems)

Solution: Contact an expert to inspect your heater and ductwork and tighten up any loose parts.

Fault 2: The heat exchanger is broken.
Do you hear a high-pitched rattling sound shortly after your heating system switches on?

If so, it might suggest your heat exchanger has a leakage. First, let’s discuss what the heat exchanger is.

The heat exchanger is the heart of your heating system; it’s the part that in fact warms your home’s air.

The heat exchanger is made up of metal coils that are heated by combustion. When cooler air from inside your house comes into contact with these hot coils, it turns warm. This warm air is then pushed back into your house, which is how your home stays comfortable.

That said, if the metal coils of the heat exchanger have a crack or leakage, you’ll hear a rattling sound shortly after the heater switches on. This is because the metal is expanding, which triggers a rattling sound.

Solution: Contact a professional to examine your heat exchanger for leakages. Sadly, if your heat exchanger is cracked, it will be very costly repair work (nearly comparable to the expense of getting a new furnace).

At South End Heating & Air we specialize in Furnace Repair and Replacement, contact us for a free consult. We’ll evaluate your system and help make recommendations for optimum value. After all, we want to keep you cool all summer long and warm in the winter. Just schedule a visit with one of our technicians to talk about how we can help with your thermostat settings. Would you like to learn more options our techs can help you with? give us a call 704-684-5339

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