Why Furnace Blower Motor Is Making Noise When Starting?

The complicated design of a furnace means that many moving parts have to come together to make it work. The blower motor is perhaps one of the most important, which makes any noise coming from it a tad worrisome to a homeowner. What are the possible causes of noise when your blower motor is starting?

Furnace blower motor noise when starting is likely due to damaged or worn-out parts. Humming, screeching, or thumping sounds are usually signs of underlying problems. Identifying and correcting the issue can get rid of the sound and also ensure the longevity of the wider furnace system.

The rest of the article will look at some of the most common causes of furnace blower motor noise. We’ll also cover other types of noise you may hear from your furnace and what each one means. 

Top Reasons for Furnace Blower Motor Noise When Starting 

When your furnace kicks up, it should run without generating any specific noise. If you often hear different recognizable sounds during each start, it’s a clear sign of an underlying problem with your blower motor.

Some of the commonly reported sounds include humming, screeching, and thumping.

Read: Furnace Blower Motor Makes Noise When Starting – Troubleshooting Guide

Some of the major causes of these sounds include the following:

In some cases, the furnace blower motor noise may be due to worn belts around the motor. Most belts become worn over time and may break if they stay in use longer than necessary.

You should keep an eye on the belts during maintenance sessions, replacing them as soon as they start to show the first signs of wear.

Loose Surrounding Bearings

The bearings around the blower motor are integral to its function. They get loose when they wear down, leading to some of the noise you’ll hear each time the motor tries to kick in.

A good furnace service technician can go over the bearings to confirm they are in good shape or to see if they are due for a change. 

Read: Why Furnace Blower Motor Hums But Won’t Start?

Age and General Furnace Condition

In some cases, the noise you hear at startup may just be the blower motor being louder than normal due to the age and general condition of the furnace.

The noise may be disconcerting, so it’s still a good idea to get a technician to take a look and confirm there’s nothing damaged or parts that need changing. Once that’s confirmed, you can ignore the noise. 

General Wear and Tear

It’s hard to pinpoint a specific sound to expect when your fan blower motor starts showing signs of burnout.

However, you can expect to hear discernable noise when the parts start to wear down and when there’s some damage. In this scenario, it’s best to get your blower motor looked at. It may need repairs or total replacement. 

Other Types of Furnace Noise and Possible Causes

Your furnace blower motor isn’t the only part in your furnace capable of causing loud noises. Many moving parts work together to produce the heat you enjoy.

Most of them can contribute to the uncomfortable noise from the unit. Identifying the possible source of the sound is important and can narrow down repairs quickly. Some of the top sounds include the following:

Read: Furnace Noise Problems

Loud Noise on Ignition

Your furnace should ignite without letting out any audible sounds. If you hear loud bangs each time you ignite, it’s best to get the noise checked out as quickly as you can to avoid costly damage. Possible causes of loud bangs on ignition include the following:

Expansion and Contraction

The metal ductwork in your furnace system will expand as soon as air starts moving through it. The result is some knocking noise or audible pops.

You’ll hear the sounds again as the ductwork contracts when the system is off. Expansion or contraction isn’t a problem to worry about—as long as you’re certain it’s the only one. 

Air Filter Problem

Your air filter looks like a minor component, but it’s far from it. A clogged air filter can cause quite a few problems in your furnace, including making it harder for air to flow through your ductwork. Audible books or bangs aren’t uncommon in this scenario. Ideally, you should replace your furnace air filter monthly.

Gas Build Up at Ignition

This is perhaps one of the most common causes of loud booms at ignition. It happens when the ignition doesn’t quite happen as it should, leading to a slight buildup of gas before the furnace finally kicks in.

The resulting boom is a mini-explosion that can damage the heat exchanger if allowed to go on for too long. That’s a costly fix you can avoid with some preventive maintenance. 

General Clicking Noises

You shouldn’t ignore general clicking noises in your furnace. They may be signs of common problems or deeper problems. 

Read: Why Furnace Is Making A Clicking Noise – Troubleshooting Guide

It’s a good idea to call in a technician to come and inspect these clicking sounds and possibly fix them. Some of the common causes of general clicking noises include the following:

Dislodged Small Parts

If any tiny parts of your furnace get dislodged, it may start rolling around your furnace as it works. It’s rarely a major problem, but if they move into other critical components, you could end up with some costly damage. It’s best to get the dislodged part out where possible to prevent further problems.

Clogged or Loose Inducer

Your furnace inducer fan can get clogged up with dust and debris, leading to clicking sounds as it works.

Cleaning the fan is part of most maintenance projects, so if it’s clogged up, it may be best to have a second look at your furnace maintenance schedule. Discuss with a qualified technician to figure out what works.

Malfunction in the Ignition System

Malfunction in the ignition system is a serious concern. Your pilot light may stop working properly, leading to failed ignition and the resulting clicking sound.

When the system finally ignites, you’re likely to hear that bang we’ve mentioned above. Any ignition system problems require urgent attention.

Loud Humming Noise

Your furnace is supposed to let out a low hum while it’s working. However, if the hum becomes too loud, it could be a sign of bigger underlying problems. Some of the common causes of loud humming noise include the following:

Loose Ductwork

You’re likely to hear humming sounds as air moves through the spaces within your ductwork.

You can solve the problem by securing the joints with sheet metal screws and duct tape. It doesn’t have to be a DIY project, though. Your technician can help plug any of these leaks wherever they may be.

Worn or Damaged Blower Motor

A damaged or worn motor is typically one of the main causes of a noticeable hum while your furnace is working. You need to get the problem sorted quickly to avoid having your furnace shut down at the worst possible moment. Call in a technician to offer guidance on the best way to deal with the problem, but you’ll have to change the motor in many cases.

Vibration From Loose Parts

Current passing through a loose transformer can produce loud humming noise. Other components around the furnace may also come loose over time from use.

Tightening the bolts and nuts holding down these parts is often enough to make the humming sound disappear or reduce significantly.

Read: How To Clean Gas Furnace?

High-Pitched Squeaks and Squeals

The blower speed is the most common culprit when your furnace starts making a squealing or squeaking noise. Adjusting the blower fan speed is typically all you need to do to get rid of the high-pitched sound. 

In some cases, the noise may be due to air whistling through your vents due to low return airflow.

The situation typically means that the blower is struggling to pull in enough air. Cleaning your ductwork, air filter, and vents can get rid of the squeal. 

Final Thoughts

A furnace is a complicated system that needs regular maintenance to work efficiently. Disregarding the recommended maintenance schedule from your HVAC technician could lead to a barrage of noises and may ultimately ground your system.

If your system is well-maintained, but you’re still hearing some noise, it may be time to consider a new furnace installation. Even the best units will start to wear out after a decade of use.