Why Are Loud Noises Coming From My Furnace?

As homeowners prepare for the winter, they want their heating systems to operate as efficiently as possible throughout the winter. They look for their unit to distribute heat evenly throughout their home and work as noiselessly as possible.

So when they start to hear loud noises coming from their furnace whenever they turn it on, it usually means there’s something wrong. But what are the underlying causes, and why are loud noises coming from your furnace? Mister Sewer, Plumbing & HVAC is here to help!

Identifying the Loud Noises

Associating the different noises coming from your furnace with a definitive cause is an important step in the process. Everything from clicking, banging, high-pitched squeals, humming, or rattling explains why you should call the top HVAC specialists in Pittsburgh, PA, to take a look. We’ll break down what each sound means and what’s causing it.

Clicking

Clicking noises from your furnace usually indicate a problem with your ignition system. When your furnace turns on but doesn’t have anything to ignite, the clicking noise is what you can expect. Possible reasons why your ignitor isn’t working properly include the following:

Faulty ignitor board not getting gas into the system
Dirty burners
Broken flame sensor
Extinguished pilot light

A broken fan motor could also cause the clicking sounds you hear.

Banging

Loud banging sounds from your furnace can usually be traced to two predominant causes — delayed ignition and expanding and contracting air ducts. If your ignition system takes too long, the gas builds up in the combustion chamber. When it finally alights, it can create a mini-explosion that can damage your unit in the process.

If your air ducts continue to expand and contract, you’ll hear the noises throughout your home, not just from your boiler. Positive pressure causes the sheet metal of your ducts to expand, while negative pressure causes contraction. If the noises are nearly constant, you may need to get the professionals to come in and inspect your furnace for possible issues.

High-Pitched Squeals

Any squealing noises coming from your furnace usually are associated with the blower. Powered by an electric motor, the components’ bearings can wear out over time due to a combination of age or overheating. The blower can overheat due to excessive dirt buildup or a faulty capacitor.

The squeal can also be attributed to a low airflow problem. This happens when the blower isn’t pulling enough air to heat your home properly. Usually, this can be traced back to dirty air filters, obstructed air vents, or damaged ducts.

Humming

While a low hum is to be expected while your furnace runs, a loud buzzing tends to point toward an electrical problem. These electric issues include a failing motor capacitor, an unlubricated blower motor, a bad transformer, or an issue with your inducer motor. Unless you’re a certified electrician with experience dealing with furnace wiring issues, call in the professionals to take a look.

Excessive Rattling

There are usually two predominant reasons you hear rattling from your furnace: a loose part or a cracked heat exchanger. When it comes to a loose part, everything from the bearings in the blower to the panels around your unit and connections in the ductwork could start rattling when the system runs.

You must get the heat exchanger looked at if you hear a high-pitched rattling when the furnace turns on. A leak in the heart of your furnace usually occurs over years of repeated use, and it’s the sound of the metal expanding as the heat passes through. Get a professional to inspect your unit, and if it is the heat exchanger, you can either get it repaired or replaced for a new unit.

Turn to Mister Sewer, Plumbing, & HVAC for Your Furnace Maintenance Needs

When you hear strange noises coming from your unit, it’s not an issue you can afford to ignore, especially if you want to keep your system running as efficiently as possible. Each loud noise has an underlying cause that can lead to more intensive — and expensive — repairs if you don’t address them quickly. Our team is here to help!