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

After a long summer, switching the furnace on to heat up your home can lead to the presence of some alarming noises. While some of these temporary noises are okay, there are times when the sound is caused by something serious. If the furnace is making a chirping noise, you should get to the source to fix the issue. 

Your furnace is making a chirping noise because of dust buildup, loose motor mounts, or worn-out fan belts or bearings. You can fix the problem by letting the furnace run for a few days, fastening the motor mounts, and replacing the worn-out parts.

This article will provide you with all the details you need to know to identify the reason for a chirping sound coming from your furnace. I’ll also explain how to fix each problem.

Dust Buildup

While a chirping sound coming from the furnace can be alarming, there are instances when the problem isn’t serious. A chirping noise can sometimes be normal, but only under specific circumstances. 

Was the furnace off for some time before you heard the chirping noise? 

If you’re like most people, you switch the furnace off throughout summer as you don’t really use it. Unless you live in the Antarctic, of course!

How To Fix

If the noise occurs after starting the furnace for the first time in a while, give it time. Let the furnace run for a few days to see if the problem goes away. 

However, it’s not guaranteed that the problem is temporary just because the furnace was off for months. There are a few more serious issues that can cause the noise. So, check on the furnace frequently until the noise goes away.

And if it does, you can relax — the problem was simply due to dust and dirt buildup. But if the chirping is still present after a few days, it’s time for further investigation. 

Loose Motor Mounts

If you discovered that the chirping sound wasn’t caused by the system being kept off throughout summer, then you should start looking inside. You first want to check the mounts that keep the motors in place. These mounts are fastened to the furnace’s housing with bolts and screws. 

If something comes loose — even just a little — it can cause an unpleasant sound when the furnace is on. You’ll hear a few different sounds, depending on what motor is loose and how to loose it is.

How To Fix

The fix is easy — you just need to tighten the loose mounting brackets using the appropriate tools. However, you’ll be working inside the furnace for this fix. Here’s what you do:

  1. Switch off the furnace.
  2. Open the furnace’s door to gain access to the main compartment.
  3. Take a close look at all motor mounts. This includes the blower, inducer, and flue line motors.
  4. Gently wiggle each motor to see if any of them are loose. 
  5. Once you’ve identified a loose motor, tighten it.
  6. Close the furnace and test it.

Worn-Out Fan Belts

Fan belts help the motors rotate the fans. They’re used in all fan assemblies in the furnace. The fan belts run continuously while the furnace is heating air, so they see a lot of wear.

When fan belts wear out, they become less efficient. There will be a reduction in the rotation of the fans. When this happens, less air flows into the ducts. There may also be problems with the flue line, creating a risk of combustion gases entering your home. 

If the fan belt wears out, it may create a consistent chirping sound during the entire time the furnace is on. As the belt continues to wear out, it’ll make additional louder, more concerning sounds.  

How To Fix

To determine if fan belt problems are causing the furnace to make a chirping sound, you need to visually inspect these components of the system:

  1. Shut off the furnace.
  2. Open up the main compartment and check all fan belts in the system. Fan belts are found in all motors. 
  3. Look for signs of damage on the fan belt, like tears and punctures.
  4. Check the thickness of the fan belt. Belts get thinner over time, requiring a replacement.

If you have worn-out or damaged fan belts, get an appropriate replacement. Here’s a video showing you how to do it:

Worn-Out Bearings

Yet another reason behind the chirping noise has to do with the engine. This time it’s the fan bearings. The bearings assist with the rotating action of a fan, and they wear out over time. 

As bearings wear out, they start producing chirping sounds, which means you should consider this particular noise an early sign of a developing problem. 

Worn-out bearings can damage the motor assembly, creating more of a squealing sound — a sign of severe damage. 

How To Fix

Replacing bearings is the only practical solution if they’re worn out. Here’s how to determine if the bearings are causing the chirping sound:

  1. Turn off the furnace.
  2. Check all bearings. There are multiple bearings in each motor assembly. 
  3. Look for signs of damage and wear. See if you can find cracks in the bearings. 

Summary

Chirping sounds coming from the furnace are annoying, but they’re often just a temporary problem that happens when you turn it on after a long time. There are also times when a chirping sound indicates loose parts or an issue with fan belts or bearings, which you must address. 

Author

  • Alanna Greene

    Alanna is an avid traveler who lives in Michigan. In addition to writing for Temperature Master, he also sells crafts on Etsy and takes long walks through the forests near her home.

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