HVAC unit makes noise

Common Noises Your HVAC Unit Makes That You Should Never Ignore

May 2 2022

America is a land of shining HVAC units. 91% of American households have at least one unit. Yet HVAC problems are just as common as the units themselves. One common problem is HVAC noise. When your HVAC unit makes noise, you need to stop and consider the situation. 

What are the most common noises from AC units? What problems do they indicate, and which problems can you fix yourself? When should you call the HVAC repair company? 

Answer these questions and you can get to the bottom of your AC unit problems in no time. Here is your quick guide.


You may hear a banging sound from any part of your HVAC unit. Banging is one of the most serious noises from HVAC units because it always signifies a major problem. 

Most bangs occur from fan blades. A blade may be bent, or it may have fallen off and started thumping against the sides of your vent. You should turn your unit off right away and talk to someone about it. 

You may hear a banging sound in your vents, far away from your compressor. An object may have gotten trapped in your vents. On rare occasions, an animal can get into a vent and start thrashing. 

You should also get an HVAC repair service. They can open your vents and see what the problem is. 


A few different things can cause rattling. If you hear rattling from a vent, a nut or bolt that connects two parts of the vent together may be loose. Take a close look at your vent and see if anything is shaking or out of place. 

If you hear rattling close to your outside unit, you may have twigs or leaves caught in it. You also may have a broken motor bearing. 

You can remove twigs caught in your outside unit by hand. If you notice a loose bolt, you can fix it with a screwdriver.

But don’t try to repair a broken motor bearing on your own. Ask a professional experienced with repairing HVAC units to come in.


Hissing always indicates a leak. It is one of the most significant HVAC unit noises because a leak can be a health concern. 

You should try to find where the leak is coming from. Take a look at your outside unit and see how your refrigerant is doing. If it is leaking, you need to call for help right away. 

You should also examine your heat pump. It may be leaking air, or air may be seeping from your ductwork.

These are significant problems. You should turn your unit off and call someone right away.


While your unit is running, you may hear a light hum from it. That is perfectly ordinary. The hum comes from the air running through your unit, and it’s a sign that your unit is working fine. 

If the humming becomes louder, you may have a problem. Bolts or panels in your vents may have come loose.

Your refrigerant piping may be loose, and the pipes may be banging against other parts of your unit. Assess the situation and decide whether or not you need someone to have a look.


As your unit starts up, you may hear a click. That’s your thermostat sending a signal to your unit and switching your device on. 

You may hear an occasional click from your unit. That’s usually your thermostat sending a signal to adjust the settings in your unit. Don’t be concerned if you hear another click at some point. 

Clicking becomes a problem when you hear constant clicking. But listen closely to how the clicking is occurring. 

If the clicking starts slow and then becomes faster, you may have an object in your blower fan. A part of your fan may be bent, or a stick may be caught between the blades. Take a look at your fan and try to remove the object if you can. 

If the clicking occurs without your unit turning on, you probably have an electrical problem. You should contact an HVAC repair service and an electrician. Be careful with how much electricity you use until the problem is solved. 

If you hear clicking outside your home, your compressor may be broken. You will need an HVAC technician to make fixes.


A gurgling sound is a rare sound to come from your unit. It usually indicates that your drain line is clogged. Your drain line carries the condensation in your unit away, so it is very important that you remove the clog. 

You can clean your condensate drain line yourself. Turn off your AC unit and then locate the drain line pan. It lies directly below the unit so it can capture any falling water. 

You can use distilled vinegar to clean your drain line. Follow good suggestions for cleaning with vinegar so you don’t damage anything. Then open the cover on your drain and see if you notice a clog.

If you do, you should pour more vinegar along with some hot water and dish liquid. Let the solution sit for 30 minutes and then flush the line with water.

Make sure you test the drain line to see that everything is okay. Turn your AC unit back on for a few hours and listen for any gurgling. If you don’t hear anything, your drain line is functioning.

What to Do When Your HVAC Unit Makes Noise

If your HVAC unit makes noise, you need to do something. A humming noise could suggest a bolt is out of place, but you can tighten the screw in. A dripping noise could mean your drain line is clogged, yet you can unclog it. 

Banging, rattling, and hissing noises indicate a major problem. You should get a professional to come in and inspect your unit for signs of HVAC damage. 

You don’t have to go far to find great AC technicians. Hanover Supply Company serves New Jersey residents. Contact us today.


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