When it comes to your HVAC system, there are some noises that are normal. These include a quiet hum or the sounds of air flowing through the vents. However, sometimes HVAC systems make new and sometimes strange noises that can become loud, disruptive and concerning. This does not have to be the case. Take a look at these common causes of noises in an HVAC system and what you can do about them:


An HVAC system that is running the way that it should normally make a soft humming noise. However, if it is clanking, that can be a sign that something is seriously wrong. Odds are that the clanking is either loose parts, like the blower motor fan, loose blades, or loose pipes, that are rubbing together.

Out of the two, clanking noises tend to be a bit more serious. This is because loose parts, if not taken care of immediately, can cause a great deal of damage to your system. And also be quite costly. If you hear clanking, your best bet is to turn the system off and call your technician.


If you start hearing a rattling noise from your HVAC system there are a few things that it could mean. If the rattling seems to originate from the outdoor unit, there is a good chance that there is some sort of debris in the system.

In this case, your best bet is to turn your system off and cut the power to the unit. This will give you the chance to remove the debris without running the risk of getting hurt. If you see visible damage to the condenser coils, the fan, or the compressor make sure to call your HVAC technician.

If the rattling seems to be an internal issue, from the furnace or another internal component, turn the system off and call your HVAC technician.


If you think that you are hearing a hissing noise from your HVAC unit, odds are that somewhere along the line, air is escaping from your system. If it seems as though the noise is coming from the walls, there is a good chance that your ducts are leaking. This is a serious issue, because not only can this cause an annoying noise, but it also wastes money. This is because the air that should be circulating throughout your home is leaking into the walls.

If this is your situation, there really is not much that you can do except call an HVAC professional. This is because duct repair is not really a repair homeowners can do on their own. That said, if the hissing is light, it could originate from your air vents. Often, when you hear this noise it is due to the fact that your filter is not “set” quite right, or that you have the wrong size filter on and it is creating the gap in the seal. If you think that this might be the situation this is a simple fix that starts with ensuring the filter is the right size and is placed correctly, leaving no room for gaps.