Scary HVAC Noises You Should Never Ignore


Sinclaire Enterprises, Inc.

140 South St., Walpole, MA 02081
P 508.668.8200 Toll Free 877.668.8822
Master Plumber License #9530,
Sheet Metal Master-Unrestricted #5442

When driving your car down the road, hearing your engine run smoothly typically makes you happy if you even think about it. However, when you notice engine noises or other sounds that are out of the ordinary, you should prioritize getting the vehicle checked by a mechanic before a breakdown occurs.

It’s the same with the HVAC system in your home. Your heating and air conditioning play critical roles for good portions of the year, keeping you and your family safe and comfortable indoors during the heat and humidity of summer and the often-bitter cold of our New England winters. 

A lot is riding on your HVAC system. When an HVAC system is functioning properly, it not only keeps you comfortable it also saves you money on energy bills, helps everyone sleep better, and even keeps people healthier due to maintaining good indoor air quality.

So when you hear strange or scary noises coming from your HVAC system, you should never ignore them. Just as your car is telling you something when it makes odd sounds, your HVAC system is saying something is broken, about to die, or needs attention when it does the same.

Let’s talk about some scary HVAC noises you should never ignore and what message they might be sending you.


A gentle hum when you turn on an HVAC system to heat or cool your home is what you want to hear. If you hear a hissing sound instead, something serious might be happening. When the hissing comes from the ducts, it could mean that air is leaking somewhere. Refrigerant leaks can also cause hissing sounds, and this is an even bigger problem.

Clicking or Clacking

A clicking sound when your HVAC system turns on and off, so that’s nothing to worry about. However, if that clicking sound is repeatedly happening, including after the system has turned off, that’s a troubling sign. Calling in a trusted pro like Sinclaire Home Services is the best thing to do here; they’ll figure out what’s wrong so things can get back to being right as soon as possible.

Banging or Clanking

A loose part, usually the blower or motor, can cause banging or clanking sounds. Since these parts aren’t going to retighten themselves, you’ll need to call in a professional technician to figure out what’s loose and whether it just needs tightening or if it needs a repair or replacement.


There are a lot of different things that can cause buzzing sounds in an HVAC system. Among them are unbalanced fan blades, broken parts, loose wiring, and an old air filter that needs replacement. However, if you’ve recently replaced, checked, or cleaned an air filter, or if you replace one and the buzzing sounds keep happening, then the problem is not an air filter that needs replacing, which means that the next step is to call a professional technician.


Anyone who’s been kept awake at night due to a rattling furnace knows how aggravating this can be. If you turn off the furnace, the house will get cold, but if you keep the furnace on, then decent rest and sleep are going to be challenging to come by. As with banging or clanking sounds, rattling sounds often indicate something is wrong with the blower or the motor. Usually, broken or worn components are the problem. You’ll need a professional technician to attend to this issue for you. If the rattling sounds get even louder while the blower runs, shut the furnace off immediately because something is disconnected. You don’t want to risk incurring more damage or having the existing problem become worse. 

Squealing or Screeching

When the bearings in a blower motor or the inducer motor become weak, squealing noises can occur, and they indicate that pieces in the motor have come out of their proper alignment. Once those squealing sounds begin, they won’t stop until the problem is fixed. In cases where the squealing or screeching sounds are constant while the HVAC system is running, the technician you call will fix the fan motor. If the sound is only occurring when the system starts running, the compressor and the motor that operates it are most likely the problems. If that’s the case, it might make more sense to replace the entire system if it isn’t still under warranty.


Gas building up in the system can cause loud booming sounds. In addition to being highly unsettling, such sounds tell you that the gas buildup could crack the heat exchanger, which would cause the entire furnace to burn out. That’s the biggest furnace repair problem and something nobody wants to deal with, so it’s important not to ignore this sound if you hear it.

If you hear any of the sounds described above or any other unusual sounds coming from your HVAC system, don’t ignore them and don’t wait; call a professional HVAC service immediately.


Call Sinclaire Home Services

For HVAC repair in Bellingham, HVAC repair in Milton, or for anywhere else in the Boston region, there’s really no one better than Sinclaire Home Services. 2023 marks our 75th anniversary taking care of Massachusetts homeowners’ heating and cooling needs, and that run alone tells you that we have a reputation for quality, professionalism, and trustworthiness.

When you call Sinclaire, you’ll get a prompt, helpful response, and soon a certified, experienced technician will be on the way to get things back to normal as soon as possible. We’re fully licensed and insured, and our technicians wear company uniforms and arrive in company vehicles so that you know who it is pulling up and who it is you’re letting into your home. If you’re hearing strange sounds coming from your HVAC system, if you need other repairs, or if you want to schedule a professional cleaning and servicing of your system, contact Sinclaire Home Services today!