Why Is There a Low Humming Noise In the Furnace When It’s Off?

If you have recently noticed that your furnace is humming when it is off, your very first thought probably was “it’s broken!”. However, humming noises don’t always signal you about the appliance being broken. There are a few more reasons why your furnace may sound like this.

And if your furnace has recently been making noises when it’s off, you should read this article to find out why it could happen. You will figure out whether it is actually normal for a furnace to sound like this and in what cases you should start worrying.

Also, we will explain what could be the reason for the low humming and buzzing sounds that are coming from your furnace, and how this problem can be fixed.

My Furnace Is Making Buzzing Noises. Why Is That?

Basically, a furnace is not supposed to produce any loud or annoying sounds if it is new and works properly. However, homeowners often complain that their furnace is constantly making low and quiet (or not quiet) humming noises. Except for being annoying, those sounds make people wonder whether everything is alright with their heating appliance. So let’s try to figure it out.

Buzzing/humming sound inside furnace – inspect inducer motor

If your furnace is making humming or buzzing noises when it’s working and even after you turn it off, there are two major reasons for that.

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• The first reason is the pilot light. See, humming can be due to the wrong adjustment of the pilot light of the blower. Try to readjust the pilot light to the appropriate level, and your furnace should stop humming
• If your furnace is humming while still being on and working, the problem is the gas burner. Most likely, it is getting dirty. So simply clean and adjust the gas burners, and you will get rid of the annoying noise!
• To avoid the humming noise problems, clean the filter of your furnace regularly to reduce the sound

These are the most common issues that you should address in order to get rid of the buzzing or humming sounds coming from your furnace when it is working or when it is off. However, there are a few more things that may result in your furnace producing the same sound effect. Below, you can learn more about each.

• Your furnace might have loose components. When not fastened properly together, they can start making those humming sounds. If there is really something that has got loose, you just need to reaffix it
• A loud hum can be produced by the electricity running in and out of your furnace’s transformer
• If your furnace is making loud and dramatic humming noises, most likely the motor fails. You will have to hire a professional to either repair it or maybe even replace it immediately
• Ductwork can also give out humming noises when the sheet metal screws holding it together wear over time

These are the most common reasons for your furnace producing low hummin, rattling, or buzzing sounds. Sometimes those noises can be rather quiet and cause no disturbance to you, but it can also happen that the furnace is banging like an old truck!

In this case, you must call a professional to come and examine the appliance in order to pinpoint the problem and get it fixed as soon as possible. Sometimes, mere fixing may not help and you will have to replace the furnace!

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How to Fix Your Furnace’s Humming Noise?

As you know now, there are multiple reasons for your furnace making low humming or rattling noises.

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But except for being aware of what exactly can cause them, you probably would like to know what to do to fix the issue and make your furnace work quietly again.

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Since there are four major reasons why furnaces hum or rattle, we will explain how those can be fixed. Remember that we will be talking about the following causes:

• Faulty motor
• Electrical transformer issues
• The ductwork that’s wearing out
• Loose equipment

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What to Do If Motor Is the Culprit?

As you already know, your furnace may start humming when the motor fails due to its age. Even if you maintain your heating appliance, it will anyway wear and tear one day simply because it is not supposed to last forever! And if you notice any sudden loud humming noises coming from your old furnace, then it is most likely the motor that’s making them.

If the cause of the sound is the loose contact of some screws on the motor, they can easily be fixed by yourself by tightening the screw to replace it. But if it doesn’t help and the furnace keeps on humming, to solve this issue, the best thing you can do is to call a licensed professional to come and check it or simply replace the motor (especially if it is old).

After replacing the motor, if you can still hear any loud humming noises, cleaning the air filters may help.

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How to Fix a Dirty Motor Of Your Furnace?

Dirt is another common cause of loud humming sounds that your furnace is making. See, when dirt accumulates around the motor of the appliance, it makes the motor hard to work properly. Thus, it starts humming and buzzing. if you found any dirt around the motor, clean it with an engine cleaner, otherwise, it may block the airflow and lead to overheating, unwanted sounds, etc.

But sometimes mere cleaning is not enough. If you clean the motor of your furnace and it is still humming quite loudly or starts humming soon after being cleaned, replacing the blower motor is your only solution.

To do it correctly, get all the tools ready first of all:

1. Hub puller
2. Screwdriver
3. Socket wrenches
4. Voltage meter

Then, follow this step-by-step guide to replace the blower motor of your furnace:

• Turn off the electrical power supply to the furnace
• Unplug the wire to make sure it’s safe to work on
• Remove the cover of the blower motor
• Disconnect the wire from the main unit
• Slide out motor housing
• Loosen the set near the motor shaft
• Loosen the screw and capacitor leads on the backside
• Unscrew the hub puller until it can fit the motor shaft
• Tighten the bolts on side of the hub puller until it grips
• Turn the hub puller clockwise till you feel that the motor is loose
• Now carefully remove the motor from the housing and install the new motor correctly
• Attach the motor belly band
• Correctly place the motor within the fan
• Slide the motor and its housing back into the furnace and secure the bolts
• Reconnect the electrical wire and restore the power unit

Of course, if you are not quite sure that you will manage this task yourself, you can ask a more experienced friend or family member to help you out, or simply hire a professional to do it for you.

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What If an Electrical Transformer Is the Cause?

If a problem for you hearing humming noises from the furnace is the electrical transformers, you will need to check them first of all to make sure the noise is really coming from there.

See, the transformer can make a low humming noise and it’s quite normal because the electrical current passes through it. However, if you hear loud noises from the electrical transformer, then replacing it is the only and best solution.

Before replacing the transformer, you need to turn off all power going to the furnace.

Then, with a few easy steps, the existing transformer can be replaced with the new one:

• Cut the four wires connected to the transformer with a wire cutter.
• Next, You need to remove the screw around the transformer with a screwdriver and you also need a socket wrench depending on the size of the transformer.
• Place the new transformer and screw it correctly without any short.
• Connect the four wires according to the old one. Now, it’s all complete
• Тow you can run the furnace and check for any issues

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What to Do If It’s Your Ductwork to Blame?

If you have been using the furnace for several months or a year, the ductwork will become loose. It often results in vibrations while running the appliance. If your furnace is making humming noises, try to check the ductwork to make sure it is properly tightened.

If you find any loose joints, those can be fixed by tightening the ductwork or replacing it with screws for tightening. To save you time, contact a professional expert for solving this issue.

Humming Noises May Come From Loose Equipment

This is the case when your furnace is simply old, which is why it is making loud humming and/or rattling noises. It sounds like this simply because of the loose equipment. So if your furnace is old enough and moreover, if it has not been inspected for a while, then it’s loose equipment that is making those loud humming noises.

Like this, you are now aware of the basic causes of humming that may come from your furnace. And since you know how those issues can be fixed, you will be able to deal with the malfunctioning or simply dirty heating appliance and bring it back to work pretty fast.

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Is It Normal For a Furnace to Make Humming Noises?

People often wonder whether it is normal for their furnaces to give out any sounds. At this point, we would like to clarify one thing at once: see, if your furnace makes a dull humming sound when it is working or shortly after you turn it off, it is absolutely fine.

Noisy Furnace? – Top 5 Fixes | Repair and Replace

There are also a few other noises that may be coming from the furnace. Most of them are:

• Banging
• Clicking
• Humming
• Buzzing
• Rattling
• Whistling

But any loud humming or rattling sounds that last for a long period of time or when the furnace is off are not good because they point to major issues in the appliance. You can also hear loud banging noise from the furnace when it turns off.

Typically the sound is coming from metal pieces of the appliance. If you hear any unwanted noise from the furnace that is way too loud or it lasts way too long and won’t stop even when the appliance is turned off, contact a licensed professional for inspecting the issues.

Well, now you are aware of all the nuances that may come with the humming furnace. We told you why your heating appliance can produce this kind of sound, what can lead to these noises, and what could be done in order to fix the problem.

So the best thing you can do is to maintain your furnace properly, clean it regularly, and of course, get it inspected by a professional to pinpoint any problems at the earliest stage! It will help you keep your appliance well-working longer and save you from unplanned expenses for repair or replacement.

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