We spend $20 billion on HVAC equipment each year.

With regular maintenance, your furnace is an investment that will last a long time. But sometimes things go wrong, and when this happens the first sign is often a strange noise. But it can be hard to pinpoint what exactly is causing the noise, and how to fix it.

Don’t worry, we are here to help. Read on for the most common culprits and how to silence your loud furnace.


If you can hear a rattling noise coming from the furnace, it could be that a panel or screw is loose. You can try to fix this yourself.

With the power off, use your screwdriver to tighten your panel screws. This may end up fixing that rattling sound. If this doesn’t fix the rattling, there could be a more serious and dangerous problem. Rattling can also signify a faulty heat exchanger with a leak or a crack in it.

You should address it as soon as possible as it can lead to carbon monoxide leaking into your property. Contact a professional immediately if you cannot fix the rattling noise by tightening the panels and screw.


If you’re hearing a loud screeching sound along with a rattle when you turn the furnace on, this could be the bearings in the blower motor, or the motor itself.

The motor requires regular lubrication to maintain top performance. Otherwise, the fan can seize up, which can be costly to repair.

If you are familiar with how to do it, you can add lubrication to the motor yourself. This can be an in-depth DIY project, requiring you to carefully remove the motor so keep this in mind. It can be better to contact a professional for a full inspection, oiling, and any other maintenance or check-ups.


If you hear a loud clanking or scraping sound, like metal-against-metal, this points to a serious problem with the blower wheel. The most common issue is the blower wheel coming loose. The noise is made when it hits against the blower house casing.

If you hear this sound, it needs addressing straight away. You need to turn off your furnace immediately and wait for a professional to do a full inspection.

If you follow these steps and catch it early, you should only face minimal damage and repair needs. If not, the blower fan can completely break and need replacing. Your service professional will be able to advise on what action is needed.


If your furnace has a belt driven motor, if this comes loose it can cause a squealing sound. Another reason for this sound could be that the shaft bearings or other moving parts are dry.

When you do your maintenance checks, make sure that all the moving parts are lubricated. This will ensure your furnace is working with maximum efficiency.

As time goes on, your blow belt will need adjustment or replacement. You can make adjustments on your own, but you shouldn’t attempt to replace a damaged belt by yourself. It is best to contact a professional to inspect and carry out a full replacement.


If you’re hearing a loud banging or booming sound, this could mean your furnace has dirty burners. This is dangerous as it can delay the ignition. The delay on ignition causes gas to build up, and this causes the boom when the ignition is turned on. Your burners should be regularly cleaned to avoid this issue.

Another cause of a loud boom or bang is an unbalanced air-to-fuel ratio. To work properly, your furnace needs to have the right mixture of air and gas. If your burners are clean, you will want a professional to inspect the situation. They will be able to make the proper adjustments.

A boom or thudding sound could also be the metal air ducts contracting and expanding due to temperature changes. This is a natural process and does not suggest any damage. If it becomes annoying, some solutions are sealing and insulation, a duct replacement or an air filter replacement.


A sign that your duct is too tightly secured is hearing a squeaking sound when you walk on the floor near the furnace. It could also be a sign that the metal panning may not have been secured correctly.

You can help this by reinforcing the duct. Listen and find the weak spot. To fix this you can try screwing a thicker piece of metal onto the weak spot or you can re-hang the duct.


If you can hear a whistling sound this could be gaps in the duct. Try to locate the source of the whistling. Often, it will be a small hole or gap near the connecting point between the furnace and duct. The whistle should stop once this is patched.

If the whistling has started recently, it could be a clogged filter. Even the smallest of holes can create a loud whistle. To test this, pull out the filter and see if this stops the whistling. If your filter is dirty and stopping air flow, it is a good idea to take it out while you buy a new one. It will not only reduce the noise but also prevent wear and tear on the fan motor.

Another possible cause is that your ducts are too small. A whistling noise will happen if your furnace needs greater airflow. If this is the case, then you will need to replace your ducts with larger ones.

Silence Your Loud Furnace

Now you know the common faults with furnaces, and how to fix them.

Whether you are dealing with a bang, rattle or whistle, you’ll know what is most likely causing it, and how to silence your loud furnace.

If your issue is too much for you to handle, or you just want some professional help, contact us at Williams Service Company. We have been a leading provider of heating, ventilation and air conditioning services since 1979.