Furnace Noises and What They Mean: Tips for Homeowners

With the season change from air conditioning to heat, homeowners who need to switch on their furnace will notice an array of different seasonal noises coming from their furnace. Some of these noises are completely normal and some may be cause for concern. In this article, we will go over different furnace noises and what they mean. 

I’ve been working with various styles of furnaces for years. From oil, to gas and electric, I have serviced, repaired, and installed lots of different furnaces. Like any mechanical system, your furnace will make different noises. There are normal furnace noises that give us no cause for concern. And some furnaces may make a popping noise when fired up or even a furnace grinding noise.

If your furnace is making strange noises that you aren’t used to hearing, give us a call at (610) 446-7877, or contact us online so we can come out and take a look… or a listen. 

What Are Normal Furnace Noises?

Does your furnace make popping noise when turning on? It is normal to hear a pop or click when a furnace initially starts up. That initial pop is usually followed up by a low hum or the sound of metal expansion as the different metal parts heat up.

There are some normal furnace noises you can expect to hear, but there are also some noises that do cause concern. And if left unexamined can open the door for some mechanical failures. Let’s sort them out.

12 Common Furnace Noises and What They Mean

In this article, I will review and explain the likely causes of the following noises:

• Scraping Sound
• Rattling
• Thumping
• Clicking
• Squealing
• Booming
• Buzzing
• Vibrating
• Clanging
• Pops
• Grinding
• Knocking

Read More: Common Furnace Smells

Scraping

Among your furnace’s many mechanical parts is a blower wheel that helps to push the warm air through the system and into your home. A scraping noise may indicate a broken or loose blower wheel.

This is one of those times when you need to be proactive and turn your furnace off immediately to prevent additional damage. Call in an HVAC service technician in for an inspection to confirm the cause of the noise. If left unattended, it can cause more expensive and costly repairs down the road – not to mention the annoying noise will persist.

Rattling

Rattling sounds typically mean that something is loose. It could be as simple as a loose access panel or door. This may be a DIY fix. Check all of the exterior access panels and furnace doors for loose screws or improperly fitted panels.

If that does not provide you relief, it may be an internal part that would require the need for a service call. Furnaces are complicated mechanical systems with constantly moving parts that can become loose over time. If you feel that this is an internal issue, it’s time to call in a technician.

Thumping

Thumping noises can occur when a build up of dust, pet dander and debris can off balance the blower wheel. A general lack of maintenance – i.e. – changing out the air filters can cause this build up.

Check your air filters and change them out. If this does not solve the problem, it is time to call in your technician.

Clicking

The ignition system on your furnace will create an initial clicking sound when it first fires up. If the sound persists throughout the heating cycle, there is a problem with your furnace.

Repeated clicking often means there’s a problem with the ignition system. If your furnace won’t ignite, it may produce a clicking sound as the igniter struggles to come on.
Ignition system problems are usually caused by issues like a dirty burner, a defective ignition board or valve, or a damaged flame sensor. Besides the ignition system issues above, compressor or control panel issues may also result in clicking sounds. Additionally, a faulty fan motor can cause clicking sounds. It’s best to contact a professional technician to inspect your furnace if it makes repeated clicking sounds.

Squealing

Squealing noises are usually an indication of a slipped or worn belt, usually around the blower motor and fan. A small adjustment may fix the problem. But it is best to contact your HVAC company for a complete diagnostic check up to look for other worn parts.

Booming

A gas furnace that booms, bangs, or pops when it first turns on has a problem called delayed ignition. This issue typically occurs when you haven’t used your furnace for a while or if the equipment is overdue for maintenance.

Buzzing

If your furnace produces a loud humming or buzzing sound, there could be an issue with the motor. There may also be something wrong with the fan. It can be something as simple as a loose screw, loose door, or improperly installed furnace filter.

Vibrating

The most common cause of furnace vibration are loose parts, which can occur due to wear and tear. Inspect the furnace regularly to ensure that all screws, brackets, and other fasteners are secure and aren’t coming loose parts.

Clanging

Clanging noises typically come from metal on metal. Turn off your furnace immediately and call your HVAC technician.

Pops

Banging and popping sounds are normal furnace sounds of metal expansion. They can also indicate dirty burners causing delayed ignition. If the sound persists, contact a professional.

Grinding

Furnace grinding noises indicate worn out bearings. That is never good news. Shut down your system and contact your technician immediately.

Knocking

The most common cause is air bubbles trapped in the lines. The solution is to “bleed the lines.” This involves draining the lines to remove the trapped air and should be done by a licensed professional.

FAQs

I have put together a few answers to the most frequently asked questions that folks looking for expert heater repairs in Havertown, PA have asked us.

Why does my furnace sound like an engine?

Blocked or closed vents can cause increased sound pressure as the furnace blower motor and fan push air through, resulting in a “jet engine” sound.

Should you be able to hear your furnace?

Most furnaces only generate a minimal level of noise while operating. If your furnace is loud enough to drown out conversations or be heard from several dozen feet away, there may be a problem.

Why is my furnace so loud now?

A loud furnace is a sign that it is working too hard. Check your air filters to make sure air is able to flow properly.