Furnaces can make a variety of sounds. Blowing noises may be the normal movement of air through your HVAC ductwork and vents. But there are other reasons why your furnace may be making a loud blowing noise. We’ll explain when you should be concerned, and other noises that indicate a problem that may require furnace repair.

The Furnace Is Rumbling

A slight woosh or roar at the end of a furnace cycle isn’t uncommon. But loud rumbling can be a bit of a concern. It can mean fuel is still burning after the burners shut off. A rumble doesn’t always sound like a big deal, but don’t ignore it. You risk being exposed to carbon monoxide, so call an HVAC repair contractor right away.

What to Do If My Furnace Is Humming

If your furnace is producing a low humming noise, this is no cause for concern. Most furnaces do while they’re on, and chirping, rattling, crackling, or pinging are generally normal. But a louder humming noise or buzzing sound can mean the motor or fan may be damaged or wearing out. These sounds should be investigated by an HVAC technician, especially for electrical issues.

Causes of a Thwapping Noise

A thwapping sound may be subtle amongst the backdrop of normal swooshes and hums. Nonetheless, it can indicate something is interfering with the furnace’s blower blades. The cause often isn’t alarming, but wear and tear may be affecting the motor, forcing it to work harder. In turn, your furnace may run less efficiently.

The Furnace Is Whistling Loudly

If your furnace is making a loud blowing noise that morphs into an irritating whistle or squeak, a blower problem may be the cause. While reduced airflow due to a dirty or clogged filter can make these sounds, a loose bolt or component can as well. Low airflow will strain the motor as it tries to draw in more air. Try changing the air filter or opening all the vents, but if there’s still a high-pitched whistling sound, repairs might be necessary.

The Furnace Is Booming and Banging

If the normal sounds of your HVAC system turn into a booming, chances are there’s an air pressure issue in the ducts. They may be undersized. In this case air pressure can cause them to expand and contract. As metal pops in and out, it creates loud bangs or pops. If not fixed, the issue can cause damage to your ductwork and vital HVAC components. 

Banging or booming sounds that occur when starting up the furnace are more dangerous. These can indicate a delayed gas ignition, which can happen due to a faulty component or improper gas to air ratio. The bangs you hear are actually small explosions. Gas is building up, which means the heat exchanger can be damaged and your safety may be at risk.

Other Furnace Noises to Be Concerned About

Screeching sounds can indicate a motor or fan belt problem. Clunking or bumping can mean a belt is cracked. If your furnace is whining, it’s time to have a contractor check the system. 

Clicking sounds are normal as the furnace fires up, but if they persist throughout the heating cycle, the igniter may be struggling to turn on. Faulty fan motors can cause clicking sounds, but the furnace should be inspected by a professional for dirty burners, damaged flame sensors, or problems with the ignition board, control panel, or a valve.

If you have a high-efficiency gas furnace, a gurgling, dripping, or splashing noise can mean the drain pan is clogged or drainpipe is blocked. Watery sounds from vents or air ducts can indicate moisture problems that can lead to mold and structural damage. It’s therefore always important to call an HVAC contractor for unusual noise.

Call Hansen Air Pros to Investigate Furnace Noise

Our licensed technicians are experienced in furnace repair and can determine the source of any loud blowing noise or other sound your system is making. Once they quickly diagnose the problem, you’ll receive an upfront quote. We strongly suggest calling as soon as there are signs of trouble, as it can prevent breakdowns and more heating repairs. Don’t be left in the cold during a Mobile winter. Contact Hansen Air Pros at 251-551-9245; we’re available 24/7 to help.