A noisy furnace can be disruptive and downright annoying. There could be many reasons for your furnace making loud noises, but it also depends on the type of noise it’s making.

Whether it’s a banging, squealing, rattling, or anything in between, it’s important to get it fixed as soon as possible so you don’t face bigger issues down the line (because nobody wants a broken furnace in the middle of winter).

But how do you know when it’s necessary to call a professional? What can you diagnose and fix yourself, if anything? Read on to learn more about why your furnace is making loud noises and what might be causing it


A clicking noise usually means a problem with the ignition system. This system is responsible for creating combustion, or heat, and the clicking noise comes from the ignitor struggling to light itself.

Common ignition issues that cause a clicking sound include:

  • No gas is reaching the system due to a malfunctioning ignition board or bad valve
  • Dirty burners
  • Broken flame sensor
  • If your furnace is older, it could also mean a broken thermocouple or an extinguished pilot light

In this situation, it’s best to have a professional inspect for the issue.

Squealing or Whistling

A squealing or whistling noise coming from the furnace usually points to an issue with the blower. This part is powered by a motor with bearings that can wear out as a result of age or overheating. Overheating itself is usually caused by a build-up of dirt or a bad capacitator.

This sound can also be caused by low airflow, meaning that the blower is struggling to pull enough air to be heated. Common causes of airflow can include:

  • Dirty air filter
  • Closed air vents
  • Dirty or damaged air ducts

If you’re experiencing a squealing or whistling sound, you should try changing the air filter. If that doesn’t work, then calling a professional in to examine the problem is going to be the best thing you can do.


If your furnace is rattling that could mean it has a loose part, or that the heat exchanger is cracked.

Loose parts are bound to happen in any piece of complex machinery. As the machine runs and moves all of its parts, things can be knocked out of place or undone at any given point. All you can really do here is contact someone to examine your unit and tighten any loose screws or other parts of the furnace.

Cracked Heat Exchanger

If the heat exchanger is cracked, you’re more than likely to hear the noise right after it turns on. This sound stems from the heat exchanger leaking fluids, which is going to dictate how effective your home’s overall heating is.

It’s the heart of your furnace, and if the metal coils have a crack or leak in them, the metal is going to expand and cause that noise every time the unit turns on, causing a rattling noise.


The source of this problem can come down to two sources: delayed gas ignition or expanding and contracting air ducts. If you notice banging, it’s important to pay attention to the timing of when it happens.

When It First Turns On

If it happens when your furnace first turns on, that might mean it’s not lighting properly. If your furnace doesn’t light up as it should, gas begins to build up in the combustion chamber. When the furnace finally does light, all of that built-up gas causes a mini-explosion — harming your furnace in the process.

The best thing to do is call a professional to examine your ignitor, but the issue could be a low gas supply or dirty or misaligned burners.

Intermittently While Furnace Is Running

If you hear banging by your furnace or throughout your house while it’s running, that probably means it’s your air vents expanding and contracting.

Air vents are made of sheet metal, which means this a pretty normal occurrence. As hot and cool air gets pushed through the metal vents, the material expands and contracts, which can cause banging noises.

If the sounds are frequent and distracting, however, that could point to a dirty furnace filter, closed or obstructed vents, or even undersized or dirty ductwork.

In both situations, unless it’s a dirty air filter, it’s best to contact a professional to examine your ductwork. If it’s simply a dirty air filter, you should replace it.

Humming or Buzzing

A light hum is normal when your furnace is running, but if you hear a loud hum or buzz while your furnace is running, that could mean an electrical problem. The most common causes of this problem include:

  • Aging or unlubricated blower motor
  • Faulty transformer
  • Bad inducer motor

The best thing to do in this situation is to immediately call a professional to get it inspected.

Remember These Reasons for Your Furnace Making Loud Noises

When you take the time to remember the reasons for your furnace making loud noises, you make it easier to recognize and diagnose any potential problems that may arise — especially during the colder months.

Sometimes, however, it’s an issue that you just can’t fix yourself. When this happens, it’s best to call in a professional like Guy’s AC and Heating! When you trust a professional to fix your furnace, you’re ensuring that it has the best quality of life and care, and it’s going to give the same right back.

Contact us at any time of the day for 24-hour service repair in New Caney or The Woodlands, TX.