Skip to Content

Furnace Making Siren Noise? 4 Common Causes (+ Fixes)

A siren noise coming from the furnace is startling and bothersome when trying to wind down or get to sleep. You don’t want to turn the furnace off, as that will make your house too cold, but the noise keeps waking you up at night. So, what’s causing the siren noise in your furnace, and is there a way to fix it?

Your furnace is making a siren noise because of a worn-out draft or blower motor, a loose blower fan, or the transformer is adjusting airflow. To stop the noise, investigate and fix the draft and blower motors and fasten the blower fan. If the transformer is making noise, you can’t do much about it.

I’ll help you find out why your furnace is making a weird siren sound and explain the steps to take if you want to eliminate the noise.

The Draft Motor Is Worn Out

The draft inducer consists of multiple parts. The main parts are the motor and the fan, both of which could be the source of the siren noise. 

When you switch the furnace on, the ignitor ignites the gas, and the draft inducer powers the fan to pull in air from the compressor located outdoors.

The motor runs continuously as the furnace is heating your home. Some level of wear on the motor is expected. Sometimes the motor wears out sooner than expected, especially if it’s not maintained regularly.

There are several moving parts in the draft motor. As the device becomes more worn out, you might notice it’s starting to become noisy. The specific noise depends on what part of the draft inducer is damaged. 

How To Fix

Some people have successfully repaired worn-out draft inducer systems. While that may be possible, it’s generally only a temporary solution. It’s a better idea to replace it instead. 

But before we get ahead of ourselves, you should first make inspect the draft inducer motor to confirm it’s worn out. 

Pay close attention to the timing of the siren sound. Also, can you hear anything in addition to the siren sound? 

The sound will usually be present just as the heating cycle initiates. 

To replace the draft inducer motor, consider getting the entire setup, including the mount, the motor, and the fan. Since the motor is worn out, there is a good chance that the fan is close to dying too. By replacing the entire setup now, you can prevent problems in the future. 

The video below will help you understand if and how to replace the draft inducer fan motor:

The Blower Motor Is Worn Out

The blower fan is the next part of the furnace you want to focus on. After testing the draft inducer assembly, see if there are any problems with the blower fan. 

The blower fan plays a similar role as the fan on the draft inducer. While the draft inducer pulls outside air, the blower fan pushes the heated air into the ducts. 

Due to the fast rate that the blower fan rotates at, it’s susceptible to wear over time. To be more specific, the blades wear out first. Depending on how worn out they are, the blades can get quite noisy. Moreover, a small crack in one of the blades can create a loud siren sound.

How To Fix

Just like a worn-out draft motor, it’s best to replace the blower fan. You’ll save time, effort, and even money if you replace it instead of repairing the blades with glue.

But you should first inspect the blower motor and the blades. Follow these steps:

  1. Shut off your HVAC system.
  2. Open up your furnace.
  3. Locate the blower fan. The fan is situated close to the beginning of the ductwork. 
  4. Inspect the fan. 

Do you see wear on the blades? If that’s the case, replace the complete unit. This is the easiest way to get rid of the ear-piercing siren sound. 

The following video will walk you through the steps to replace the furnace blower fan:

The Blower Fan Is Loose

Metal-on-metal friction is often described as a squealing sound, but sometimes the pieces barely touch each other. When this happens, you often end up with a high-pitched siren sound.

Several parts of your furnace are made of metal. Most of these parts are isolated from each other in some way to reduce noise and vibrations.

The blower fan should be your primary suspect due to its placement in the furnace. If the blower fan moves out of position, it may slightly touch the sides of the furnace. When this happens, you guessed it — there’s a siren sound!

How To Fix

Fixing this issue might be as simple as fastening the blower tightly. Here’s how to do it:

  1. Shut off your furnace.
  2. Open up the furnace.
  3. Locate the blower fan.
  4. Check to see if it’s loose or if there are any parts in the blades’ way.
  5. Fasten the screws on the blower if they’ve come loose and move any parts out of the fan blades. You can use duct tape to hold cables and other components in place.

The Transformer Is Adjusting Airflow

When the furnace starts making weird siren noises, we often jump to the worst conclusions. However, the issue sometimes isn’t even serious. In fact, siren sounds coming from the furnace can be a normal part of the HVAC’s operations. If the siren sound isn’t too loud and you don’t hear it continuously when the furnace is turned on, it’s probably the transformer.

In newer furnace models, a transformer will automatically adjust the current pulled in from the outside. When this happens, you’ll hear a humming sound that might resemble a siren. 

However, you should still inspect the furnace to ensure everything is in good working order.

How To Fix

If the siren sound isn’t something that causes you to lose sleep and only happens occasionally, there’s no reason for concern. Pay attention if the sound changes, lasts longer, or gets louder. In that case, you want to take appropriate action, starting with the three potential causes I’ve outlined above. 


A furnace making a siren noise typically isn’t a sign of something to be concerned about. A few different parts can make noise as the furnace is heating up. If the sound doesn’t go away, it could signal damaged parts or excessive wear. 

Although it’s tempting to open up the furnace and fix the problem yourself, you should consider contacting a professional instead.


  • Vincent Steele

    Vincent is a freelance writer based in Santa Ana, California. When he isn't writing articles for Temperature Master, he can be found biking or hanging out with his cat, Shelly.