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Why Is my Air Conditioner So Loud?

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Making Sense of the Noises Made by Your Air Conditioner

If you’re reading this post, it’s probably because your AC is making some crazy noises lately that you’re not used to.  Or you just moved into a house and the AC has never been used until now, and of course now it’s making strange noises.

Of course, it is a machine, and machines make noise.  But why is this thing getting noisier and noisier every summer?  Today I want to share some things I’ve seen out in the field working on other people’s AC systems that might help you isolate where the noise is coming from and some possible reasons why your AC is so loud.


Your air conditioner is very likely on the side of your house.  For some people it’s on the roof.  And for obvious reasons, a roof mounted AC will definitely make some low consistent vibration because its mounted to the roof joists, which are connected to the wall studs, and the rest of the house.  So, for those of you with rooftop air conditioners or complete package units that are so common here in California, that is something you may be stuck with as long as it’s up there.

Also, as I’m sure you already know, these are machines and machines make noise.  Typically, the older they get, the louder they get.  Understanding that, let’s dive into some real issues you might be experiencing on systems that aren’t 20 years or older.

Breaking It Down

I want to break this into two parts:  Things you can fix yourself, and things you might want to have a real HVAC technician look at.  Notice I said real technician, and not a person dressed like a technician who is just there to sell you a new system.  These deceiving salesmen and saleswomen are only in it for the money and have no interest in saving your system.

Remember, if the parts are available, and yours very likely are, or can at least be retrofitted with correctly matched universal parts, it can be repaired.  You’re in charge.  Like I always say, your system is designed to last about 20 years before you start to consider getting a newer system.  But, it’s really about where YOU want to put YOUR money and not about the technician’s ideas.

Here are some loud noises you’ll probably need a professional to address:

A Loud Compressor

An AC that sits on the side of your house only has a few parts in it that will make some crazy noises.  Inside the shell of that outdoor unit is a compressor, a fan motor, and an on/off switch called a contactor.

The biggest part, the compressor, pumps the refrigerant through your system much like your heart does the blood in your body.  This pumping requires two spiral plates to rotate in an elliptical motion.  Sometimes those plates (more commonly called scrolls) can chip or come out of alignment creating the loudest, most awful noise you’ve ever heard, especially if it happens at night when you’re sleeping.  It’s a grinding noise or loud clacking noise that cannot be missed.

We can’t just take off the cover and look inside to fix it  It’s a hermetically sealed part that can’t be opened by anyone.  If this noise can’t be fixed from outside the compressor, you will likely agree with your technician when you’re told it needs to be replaced.

An Unforgettable Noise

I personally remember a house in Coloma, CA that was doing this.  The loud noise never stopped for the customer as they ran their AC.  It wasn’t even cooling the house!  It was just running and running and running.  As we approached the unit, on the complete other side of the house, it got louder and louder.  After some testing, I noticed the compressor wasn’t pumping like it should, yet it was still making this loud noise.  This was THE loudest air conditioner I have ever heard.  It was a 10-year-old Bryant AC, so we changed that compressor out, and the system ran fine from there on out.

I’ve also come upon an AC where the compressor — one just like we were talking about — wasn’t out of alignment or broken, but had an internal part called a bypass stuck open.  This created a loud squealing or screaming noise indicative of high pressures and high heat inside that compressor.  Before replacing this part though, a technician should determine if the refrigerant pressures within the system are adequate, as well as some other tests.  Whatever the solution, be aware of some noises that this compressor makes.

Noise from the Fan Motor

Another time we might have to replace the part making the noise is on the condenser fan motor.  That’s the fan blade you’ve probably seen that spins on the top of your AC when its running.  I’ve come out on a house before where the motor that spins the fan blade is making a high-pitched whistling noise.  As I looked around the AC, my ears and eyes finally isolated the noise coming from this motor.

Every AC fan motor has ball-bearings that help the motor shaft spin.  But these bearings are sealed and can’t be accessed to lubricate them, which would likely solve the problem.  So, in this case, the motor must be replaced if you want the loud noise to cease.  Finding the right motor can be tricky, so it’s probably best to let a qualified technician do it.  Just putting a motor with the wrong speed setting will cause cooling issues you won’t be happy with.

A Buzzing  Contactor

Your AC has an on/off switch called a contactor.  The thermostat inside your home tells it when to switch on and off by sending a low voltage signal.  To plates come together at that very moment to allow the high voltage though to the parts we were just talking about before:  The compressor and the fan motor.  As the years go by, pitting caused by the high voltage arcs happening between those two plates as they come together can get to a point where the two plates won’t come together all the way creating a loud buzzing noise.  Not as loud as that compressor I was telling you about earlier, but loud enough to get your attention.  Getting into the electrical panel of an air conditioner can be intimidating and the potential for an electrical shock.  Again, making a mistake here can lead to more expensive problems.

What You Can Do

Let’s review some loud noises you can likely isolate and fix yourself.  If you don’t feel comfortable doing it, just call Fox Family Heating & Air and our techs will be happy to fix this stuff for you.

Make it Level

If your system starts making loud noises, a good first step is to make sure the unit is level.  If the AC isn’t flat, oil inside the compressor might not be lubricating the way it should be.  Just be careful not to bend the copper lines coming from the wall to the AC.  This may strangle the refrigerant and cause more expensive problems.

Check for Debris

Next, sometimes sticks and leaves can block the fan blade on top of the AC from spinning, which causes some strange noises with the AC.  Go outside and remove any sticks or toys that are preventing the fan blade from spinning.  The damage may already be done to it, but you can at least try.

Tighten a Rattling Fan Shroud

Also, the fan blade is protected by a round metal shroud that is there to allow warm air to flow out of it, but also protect people from getting their fingers inside of the AC.  Sometimes this shroud starts rattling as the screws that hold it down start vibrating loose, possibly creating a larger hole than the screws were initially sized for.  As the AC runs, the rattling can be annoying.  This tends to happen on older systems.

The solution is to install slightly wider screws that will hold the shroud down securely.  This would fill the hole better and crate less noise.  Another trick we like to do is get these little rubber isolation pads and use them as shims to help dampen the vibration between the shroud and the frame of the AC.  This can really help in reducing the vibration or rattling noise on your aging system.

How to Prevent These Problems

Preventive maintenance is key.  If Fox Family can get out to your system twice a year and do the necessary checks and clean your system, we know we can make your system last longer.  A clean system is a healthy system.  But if you don’t want to hire us to do these checks for you, no problem.  Here are some things you can do on your own to help your system out.

About Filters

Changing your filters as needed.  I always say if your filter isn’t perfectly clean, it’s time to change it out.  The filters we buy at my house come with a cardboard trim around it with some white mesh or fiberglass as the filter media.  At about $7 a 3-pack, they’re the cheapest filter sold at the store.  If that filter isn’t perfectly white, then I change it out.  I’m not tied to it because I didn’t buy an expensive filter.

Some people buy these $20-dollar filters.  Its almost like they want to hang on to these filters as long as they can, even though they are brown or gray in color now.  Eww!  That’s the air we are breathing!  That’s the air the children in the house are breathing.  This dirty, dead skin, pollen laden filter is now a contaminated breathing mask essentially for your AC.  If that dirty filter were up against your mouth as you breathed in, you would definitely change it.  So that’s what I compare it to.  You get the picture.  And I’m sorry for getting too graphic there.

Another reason to change that filter is because super dirty filters can suffocate the compressor.  This can cause burnouts, clogged evaporator coils, and other cooling problems.  If the air filter is too dirty, the evaporator coil can even form into a block of ice.  This causes serious cooling issues, including loud screaming compressors that can’t circulate refrigerant anymore.

Keep It Clean

Periodically washing the AC outside unit every now and then is a good idea.  It doesn’t take much energy to do, and it doesn’t cause  any soapy solutions to do this either.  Another cause for loud squeaking noises is a clogged coil.  But if the coil on the outside AC gets clogged like a dirty air filter does, high pressures can occur in the refrigerant system, creating noise.

Please don’t use a pressure washer.  You’ll destroy the parts of the system that are crucial for air flow and heat transfer.  But you do want to use just enough pressure from the hose to start knocking off loose dirt and small debris down to the ground.   Also try to  focus on not bending any of the fins that surround the AC.  Called the condenser coils, if you flatten them, you can create some crazy noises with your AC.


I hope this has helped you understand where some of those strange, loud noises coming from your outdoor air conditioner.  If you have any questions or doubts that you can isolate the noise, let us know at Fox Family Heating, Air.  We’d love to help keep your system running for a long time!

Thanks so much for stopping by and we’ll see you on the next blog post!

Fox Family Heating & Air serves Sacramento, Rancho Cordova, and all of Northern California. If you’re looking to schedule HVAC service in these areas, give us a call!

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