Why Is Your Furnace Loud?

The amenities of our modern lifestyles all ultimately come down to providing one of two things, convenience and/or comfort. Refrigerators and laundry machines are convenient, heaters and air conditioners are comfortable. The last thing we want one of our modern appliances to do is to reduce our comfort and the peace we expect to attain while we’re safe and sound in our own homes. But sometimes these appliances don’t work as they should and that can result in all kinds of problems. One of those problems that many people find particularly vexing is a loud heater.

Furnaces are never going to be completely silent. Blowing air throughout your home is going to come with its fair share of low-grade noise regardless of how advanced and well-oiled of a machine your furnace is. But there is a point when the amount of noise your furnace is making should be a concern, both for the annoyance and the warning signs that something more catastrophic might be in store if the root of the noise isn’t solved. That’s why at this tip of the day we’re going to investigate all the reasons your furnace might be making more noise than usual and what you can do about that.

Furnace Noise: Normal and Irregular

Loud furnace noises can be the result of various kinds of problems. These noises take on different forms depending on the reason. The hard part is getting to the bottom of the cause, and from there, how the situation can be remedied. You may be able to fix some of the problems yourself; others will require the expertise of an HVAC specialist.

Loud noises coming from your furnace while it is running could be caused by any of a number of issues. For example, you may have a problem with the fan that blows hot air through your vents. That might be due to the fan bearings being worn out. In that case, these bearings will need to be replaced. If your furnace is making a loud noise just as it starts, this could be caused by a serious problem called “delayed ignition.” This occurs when unburned oil builds up in the firebox chamber and is ignited all at once. This can be dangerous, and you should call a qualified HVAC specialist immediately.

So as you can see, the causes of a loud furnace are numerous, even more so than the type of noises a furnace might make. The following sections will go over in detail a variety of types of furnace noises, what they likely mean, and what should be done about them. We’ll look at which ones can be solved by you and which will require the help of an Austin heating expert.


The first category of noise we’ll look at is that of a loud scraping, basically, the sound of metal rubbing against metal. This can be a disconcerting and annoying sound, no doubt, and if you hear a scraping sound coming from your furnace you’ll likely want to get to the bottom of the issue right away, which you would be wise to do. That’s because of all the alarming noises your furnace can make, scraping sounds and the sounds of metal scraping against metal are some of the worse kinds. You should turn off your furnace immediately upon hearing his sound.

There are generally three big potential causes of such a sound emanating from your heater. One cause for this sound is that the blower wheel came loose from the motor shaft, moved, and is hitting the blower housing. In this case, if no damage was done to the wheel or the motor shaft, it could be moved back to the proper spot and re-tightened to the motor. But the sooner you turn off your furnace and get it serviced the less likely it will be that damage will have occurred.

Another and the more likely cause is that the blower wheel actually broke, in which case it would need to be replaced. This makes a very disturbing sound almost as bad as fingernails on a chalkboard. A third possibility is that a motor mount broke, causing the entire motor and blower assembly to drop and the blower wheel is hitting the housing. In any case, please shut off the system as soon as possible when this sound is heard or the repair bill could significantly increase.

Regardless of whether this sound is due to the blower wheel coming loose, the blower wheel breaking, or the motor mount breaking and falling, professional help will be needed. These are delicate parts that need to be fine-tuned in order to prevent this from happening again.


This is a very different kind of noise you might hear from a noisy furnace and it indicates a very different set of possible problems that might be the cause. It might sound something like a whistling or a whooshing. If your furnace is whistling, one possible cause is that there may be gaps in the duct. You should try to hear exactly where the whistle is coming from. Often, it will be from a small hole near the connecting point between the duct and the furnace close to the blower. This will require the duct to be repaired. This can sometimes mean just applying more sealant to a joint in the ducts or in the case of older ducts that have become rusted and are developing holes, you may need more severe duct replacement and repair. Either way, your best bet is going to be to contact a professional and have the whistling sound checked out.

Broken ducts aren’t the only cause of such a sound though. Especially if the whistling has started recently, you may have a clogged filter, causing the fan to suck air from anywhere it can. If the filter is too dirty, airflow is going to be restricted but the force of the intake pressure is going to cause air to look for all the places it can enter. Some of these places may cause the air to whistle. Even tiny holes or spaces will generate a whistle if any significant air is being sucked through them. Determining if this is the case is luckily very simple. To test out this possibility, pull the filter out and see if the whistling stops.

If your filter is so caked with dirt that it is clogged and stopping the airflow, you will be better off taking the filter out (while arranging to purchase a new one). This is better not just to reduce the noise, but also to reduce the wear and tear on your fan motor. Dirty filters are bad for the health of your furnace and should be replaced as soon as possible. Fortunately, this solution doesn’t require the help of a heating technician. If taking the filter out solves the whistling issue all you need to do is buy a replacement filter.

Another possible cause for whistling would be that the ducts are too small. The furnace may need greater airflow and thus larger ducts. This problem would only be applicable if you moved into a new place for instance and the whistling noise has been there as long as you have.

Banging On Startup

This type of sound can be quite alarming and also differentiates itself from the other sounds we’ve gone over so far in that it generally only happens when the furnace turns on during each heating cycle. This is a concerning noise and rightfully so. If you’re hearing a banging or booming noise coming from your furnace each time it starts you need to investigate it right away.

This noise you're hearing when your furnace comes on is likely one of two things. It could be your ductwork doing what’s called “oil-canning,” that is, flexing when the pressure changes, or less likely but more serious, it could be a small explosion called a “roll-out.”

Oil-canning is the term given to one of the furnace issues that can cause this banging sound upon startup. It is the less serious and more common of the two likely causes. The good news is if the issue is oil-canning ductwork, you may be able to fix this. You should listen carefully to the furnace to see if the banging is coming from somewhere in the duct. If oil-canning is the problem, there is probably a weak spot in the ducts that needs support. You may be able to fix this by screwing a slightly thicker piece of metal across and onto the weak spot.

The other possible cause, ignition roll-out, is not very common, but it can be alarming. It’s a little explosion that will happen when the furnace starts up, or a burst of flame bigger than it needs to be. To see if the banging is caused by a gas-ignition problem, watch the furnace start-up. Leave the doors on the furnace. If you can see into the furnace doors, you should be able to see what is happening. If not, listen in order to pinpoint where the noise is coming from. Watch to see if the doors on the furnace are at all shaking. If they are, then try again with the door to the burner compartment open, to see if the banging still occurs and if you can see what happens when it does.

If you see the extra flame or shaking associated with your noise, you have identified a potentially dangerous problem and can now correct it. You should call in a professional specializing in heating in Austin. Trying to deal with the gas portion of your furnace should be left to professionals. It’s worth mentioning that newer furnaces have a “roll-out sensor” that will shut down the unit if this problem occurs. If your furnace isn’t newer though then you’ll want to shut your furnace off completely once the cause of this banging has been investigated and you’ve drawn the conclusion that it is due to roll-out.

Noisy Furnaces and Heating Repair in Austin

We know how concerning it can be when you suddenly start hearing loud and unfamiliar noises coming from your furnace. Not only is it an annoying disturbance that disrupts the peace in the household but it can be a sign of serious damage that may worsen if the problem isn’t solved. Fortunately, there are patterns in the potential noises you might hear out of your furnace. Certain types of noises typically indicate certain types of problems and with the help of this article, you should be able to take steps in diagnosing the issue. This will give you the knowledge you need to determine whether an Austin heater repair technician will be necessary.

If such is the case, consider AC Express. We have been doing heater repair in Austin for many years with many satisfied customers. We operate all around the Austin area, from Buda and Kyle to Liberty Hill and Taylor. If you need heater service in Austin don’t hesitate, call today!