Today’s modern energy-efficient air conditioning systems are built with sound dampening technology and engineered to produce very little noise.  If you hear any loud, repetitive or disconcerting noises, it is a clear indicator of an issue.  Although air conditioner noises are disruptive and annoying, they may alert you to an issue before it becomes a major problem.  The different sounds can also help us identify the issue.  Here are 12 common noises your AC might make and the issues they indicate.

Is your air conditioner making strange noises? Your AC is talking to you. And it’s saying, “help.”

We’re reviewing the 12 most common noises your AC makes and the issues each sound indicates. 


A buzzing sound can be caused by a number of issue. If you hear buzzing noises from the air conditioning equipment outside your home, the sound could be caused by a faulty condenser fan motor, a faulty compressor, or unbalanced fan blades. If a part has stopped working but is still getting electricity, a buzzing sound will happen. There are other electrical issues with the compressor that can produce buzzing noises, such as a relay switch delivering incorrect amperage to the compressor. Buzzing can also be caused by an electrical issue affecting the fan motor or debris inside the unit that are interfering with the condenser fan.

If your indoor AC unit is buzzing, it can be due to the freezing of its parts.  Many reasons can cause the indoor unit to freeze, such as the thermostat set too low, low refrigerant, etc. Buzzing noises can often be heard when ice has formed on the evaporator coils inside the central air system.

Never ignore a buzzing noise from your central air conditioning system. Be proactive and prepare for the summer season by scheduling an air conditioner preventative maintenance.

Call us if you hear buzzing sounds coming from your AC unit.  Schedule a preventative maintenance service to be proactive and keep your AC running at peak performance.


You may begin to notice a humming noise inside your air conditioner due to a defective contactor relay switch. This component is designed to start the outdoor condenser unit when it receives a signal from your thermostat. Unfortunately, you will not be able to turn on your air conditioner until this issue is inspected by a licensed technician. Do not ignore electrical issues in your system. This will cause severe damage to your central air conditioning system that will be accompanied by expensive repairs. 

Call us if you hear any unusual sounds coming from your AC unit.  Schedule a preventative maintenance service to be proactive and keep your AC running at peak performance.


At the beginning and end of each cooling cycle, it is normal to hear a clicking noise, but if you hear a continuous clicking sound while your AC is running, this is not normal. This type of sound may indicate a problem with your thermostat or an electrical problem with a relay switch. Capacitors in the AC’s compressor could also cause the clicking noise. Electrical issues should always be checked by a professional. Contact us if you think you have an electrical issue with your AC. 

Call us if you hear unusual clicking sounds coming from your AC unit.  Schedule a preventative maintenance service to be proactive and keep your AC running at peak performance.


A bubbling sound usually indicates excess moisture in you AC system. Excess moisture is usually caused by a blockage, crack or hole in your condensate drainage pipe. The condensate drain pipe removes the moisture collected by the AC and drains the moisture outside of you house. If the pipe is blocked, it makes a bubbling or gurgling noise. If the condensate pump gets damaged, it can also lead to excess moisture build up and lead to a bubbling sound.


If you hear a sound that is more of a gurgling sound than a bubbling sound, it could be an indication of an improper sealing of refrigerant lines. When air gets trapped in the refrigerant lines, it makes a gurgling sound as refrigerant moves through the lines.

Call us if you hear any unusual sounds coming from your AC unit.  Schedule a preventative maintenance service to be proactive and keep your AC running at peak performance.


Anytime we hear dripping we imagine the worst.  Where is water leaking and what damage is it causing?  If you hear a dripping sound from your AC don’t panic.  It could be moisture falling into the drip pan.  That is what it’s supposed to do.  Water collects in the drip pan and is removed from you house through the condensate drain line.  How ever if your condensate drain line becomes clogged, the drip pan can overflow and cause water to leak in your home.  Another possible cause of dripping sound is ice melting from frozen evaporator coils.  Evaporator coils may freeze due to a malfunctioning thermostat.

Hissing Noise

A hissing sound is likely the sign of a refrigerant leak.  Refrigerant leaks typically happen in the copper refrigerant lines or in a malfunctioning expansion valve.  Over time with use, the lines can deteriorate, causing leaks.  Refrigerant creates a hissing sound as it escapes cracks in refrigerant piping and elsewhere, because it is under great pressure when held inside the closed system.  Hissing sounds could also be caused by an air duct leak or a compressor valve leak.  A refrigerant leak requires professional repair, as technicians must possess an EPA license to handle refrigerant.

 Hissing can also be an early indicator of high internal pressure inside the compressor. A hissing noise will come before high pitched squealing.  See Squealing Noise.

 Squealing Noise

If the hissing noise turns into a shrieking or squealing noise after some time, it is a compressor issue.  A high pitched squealing noise coming from the compressor could be the sign of dangerously high internal pressure. You’ll hear the squealing sounds as the air conditioner first starts, and they typically last only about 10 to 15 seconds. Turn off the AC immediately as high-pressure build-up can cause an explosion. Contact us as soon as you can.

 Screeching Sound

Other problems that could sound like squealing or screeching are the fan motor bearings or the fan belt.  If the fan motor bearings lack adequate lubrication they become dry and start to produce a screeching sound.  Metal-on-metal screeching noise when you turn your AC on means the fan motor bearings have become faulty and need replacement. 

Older AC systems that use belt-driven fans, may make a screeching sound at times.  A worn out belt may become loose and slip from position, making a squealing sound as the system runs.  This type of noise is most prevalent in ducted/central air conditioners.

Rattling Sound

A rattling sound is often the sign of loose parts which could be caused by wear and tear.  If the sound is coming from the inside unit, it’s probably due to loose parts such as screws, bolts, or fasteners.  If you hear a rattling sound inside your home, but not necessarily around the unit, it could be from a closed air vent or a loose duct.  Another cause of rattling noise is sticks or twigs hitting the fan on the outside condenser unit.  You should be able to do a visual inspection and see if this is the problem.  If the rattling sound is coming from down in the unit contact us, but if there is debris on top carefully remove the debris while the unit is not running.  If that stops the rattling, you don’t need to do anything else, but if the rattling persists, contact us immediately.

Clanking Sound

Noises that sound like clanking could mean loose parts or it could indicate that the fan blades are not in balance. This issue can affect both the indoor fan that blows air through the ducts as well as the outdoor condenser fan. When the fan blades are not balanced, the blades hit against other parts as your AC unit runs. Fan blades that are not balanced can cause damage to themselves and other components.  Our technicians can balance fan blades which not only protects your AC system from damage but also increases the efficiency of the unit.

Banging Noise

Unfortunately banging sounds can only mean bad news.  Most likely banging means there is a broken part in your AC.  You may have a damaged piston, connecting rod, or broken compressor.  In any case if you hear a banging sound, you should shut your AC off immediately.  The worst case scenario is that your compressor needs to be replaced.  The compressor distributes refrigerant through the AC system removing excess heat from your home. As your central air conditioning system reaches the middle or end of its lifespan, it is not uncommon for parts to become loose inside the compressor.  If your AC is making a loud noise from inside the unit, it could be due to a broken fan motor or an imbalanced motor, causing the bangs. Replacing the motor can also be costly.  Contact us to identify the issue and discuss the best options.


AC units today are built to be efficient, reliable, and quiet.  Most AC units only make between 25 and 55 decibels of noise while they operate.  25 decibels is about the level of a whisper, and a normal conversation is about 55 decibels.  We can analyze the sounds they make to determine if there is an issue, and diagnose what the issue is.

One of the most frustrating things about owning a home is the unexpected expenses that come up at the worst possible time.  Our preventative maintenance plan helps protect you from unexpected costs.  Preventative maintenance allows us to catch potential issues before they become major problems which extends the life of your unit and keeps your AC running efficiently.