AC & Appliance News

Did You Hear That? Different Furnace Sounds and What They Mean

Heating equipment is the #1 cause of fires in US homes.


That might seem straightforward, but you might be surprised how many homeowners know none of the warning signs of dangerous house equipment. 


Furnaces are a great example of a home installation that gives you red flags before anything goes wrong, and if you aren't able to spot it, there can be real trouble. 


That leads to the question: where is my furnace noise coming from? 


Some common examples include: 


  • Bangs 
  • Humming
  • Metallic Clanking
  • Buzzing 
  • Squealing 
  • Whistling 
  • Chirping


A Helpful Tip For Furnace Noise


A basic understanding of physics will tell you friction often makes noise. This might seem trivial, but if you have this awareness under your tool belt, most issues will become immediately obvious to you. 


For example, in the case of a screeching furnace, the most common cause comes from a damaged furnace motor. Luckily there's a real solution to this. 


Beginning With A Bang!


It's not reassuring to hear gunshot sounds come out of your furnace. 


If you hear a loud bang or thud, it's often a build-up of excess gases. This happens because of a delay in your ignition. 


What's supposed to happen: your ignition goes off at the right time, burning the released gases. 


What ends up happening: the ignition has taken the day off, and the released gases have gathered, so when the ignition does go off the ignited gases do as well. 


What's causing my loud furnace? 


It's probable that your burners need to be cleaned, as this causes the delay. 


But there is an exception. 


In some cases, the bang is coming from stretching ductwork, in which case you have nothing to worry about. 


No matter what, if you can't spot the issue contact your serviceman or HVAC specialist to determine the real issue. 


Clanking/Metallic Scraping Sounds

 

Time to apply deduction again! 


Just as we looked to friction as the reason behind our furnace sounds, we can determine what's going on by listening carefully to repeated clanking. 


In the case of metallic scraping, clanking, or rhythmic friction, look to the parts of the furnace that move. 


The culprit is either the motor or blower, sometimes both. 


If the blower fan has detached it's probably banging against the casing formally holding it in place. 


Another problem may be that parts have undone in the blower fan and motor, causing everything to hit against the housing. 


These are issues for a specialist and shouldn't be overlooked. 


A Distinct Humming Sound

 

If you're noticing what is often a subtle humming sound coming from your furnace, turn to your motor. 


Say your motor is humming. This is often caused by the machine coming loose from its mount. 


Each motor in a furnace has a mount to keep it in place. When you hear a humming sound emitted that's usually the case. 


The other problem might emerge from flimsy or bending ductwork. When air passes through the ductwork wobbles making a humming sound. 


Clicking


Clicking is often the result of a flame sensor, ignition, or gas. 


A flame sensor spots a certain level of current generated from the flames heat. This registers in the sensor and then gives permission to the main gas valve to open. 


If a flame sensor, or a sensor of any kind, isn't working, this is an immediate issue that needs to be dealt with. 


If the issue involves gas or ignition: when the furnace calls for heat, the pilot will use its ignitor to fire. 


When clicking occurs and the problem is gas or ignition, your furnace will likely have problems starting up as well. 


Chirping


This is an odd one. When you hear a chirping noise coming from your furnace the problem usually comes from furnace disuse. 


Meaning you might be in luck. The furnace might just be unused to starting up. 


Another possibility: the fan belt needs to be replaced. 


Squealing


This is different than the screeching sound talked about earlier. Though a squealing sound will be a result of some kind of friction, the damage is often to a fan motor or belt. 


Like all of the sounds on this list, most damages occur from poor maintenance and time. 


Whistling

 

If you hear whistling coming from your furnace turn your attention to your furnace filter. 


The sound is the result of a clogged filter keeping air from getting through. 


This can also mean something more ambiguous: air is escaping out somewhere. 


The whistling sound might be from leaking air ducts or other instabilities in your vent system. 


Buzzing

 

Many of these problems involve loose parts when you hear buzzing it's no exception. 


If buzzing comes from your furnace it's probably due to a loose transformer box. 


The buzzing sound might be from a dead transformer box as well. 


Both of these cases are fixable. 


A dead or loose blowing motor is another cause. 


All of these reasons can be found during your next inspection. Though, if your transformer is loose there is the chance for an electrical fire. 


Take all these cases with caution. 


How To Prevent All Of This

 

The key to preventing any machine from breaking down before its due date is maintenance. 


There are some examples of quick fixes that prevent a loud furnace and save you a few bucks: 


  • Vacuum your burner
  • Make it a habit to dust off your pilot 
  • Pay attention to furnace flames. They should stay constant and appear light blue
  • Make sure, at the very least, to maintenance your furnace annually.

 

Right below maintenance is making sure you have good parts. 


When both these points are combined your furnace, like any machine, is better off. 


Still, it's important above all else to call your repairman to take care of your heating unit. 


What's Your Next Step?


By now you're probably tired of hearing the circus of sounds coming from your furnace, right? 


Well, now you have the awareness to spot which furnace noise indicates which problem. 


Take this knowledge and contact a reliable service that will get rid of those pesky sounds and put you at ease.  

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