Why is My Air Conditioner So Loud?  How to Fix a Noisy AC

When someone asks us, “why is my air conditioner so loud?”  I often respond with, “why is your truck so loud?”  Just as with your truck, a noisy air conditioner is a complex piece of machinery with many moving parts, all of which interact with each other.  So, figuring out why your air conditioner is so loud is far too complex a question to address all in one article, so we will instead focus on a few of the most common causes for a noisy AC.  Just as with your car, if it starts to make a harsh, grinding sound, then it’s probably best to leave it to a licensed HVAC technician.  But that does’t mean you should rush to your phone the second you hear your HVAC unit squealing.  Those of you who read our articles regularly, know that we are a small, U.S. Veteran-Owned HVAC company in Southern California, and pride ourselves in giving people honest, straight answers to their questions.  Case-in-point, often times you can avoid a costly AC repair and fix your own noisy air conditioner; we aim to help you do just that.  In general, a change in the way your AC sounds is a bad sign, but that does’t mean that it isn’t an easy fix.  Here are a few things for you to think about when your air conditioner gets loud, most of which you can do yourself with just a little bit of time and some basic household tools.

why is my air conditioner so loud

 Why is My Air Conditioner So Loud?  First, Ask Where…

The first part of figuring out why you have a noisy air conditioner is to get an idea of where the sound is coming from, and what type of sound it is.  Is it coming from the compressor, or is it the fan itself?  What about the condenser coil which also has a fan over it?  In order to understand this, you need a basic understanding of how your AC works and what parts it has, so if any of this is new to you then start here – don’t worry, it sounds worse than it is:

WARNING: Before doing any maintenance on your noisy air conditioner, first start by turning your HVAC circuit breaker to the OFF position in your main CB panel, remove the disconnect (if applicable), and turn your air conditioner off with your thermostat:

why is my air conditioner so loud CB

Step 1 – Is the Fan Motor Squeaking

Is the sound coming from your fan motor?  Split AC units (See: What is a Split Air Conditioner?)have an inside and outside portion, either of which works under the same principle – they both have a fan with a motor.  To examine your noisy air conditioner, remove the outside casing to reveal the inner part of your AC unit – you will notice the fan located just in front of the coils.  If this is your problem, remove any debris from the unit and check the fan blades for dents or dings.  A common problem when you are dealing with a squeaky fan blade is the dirt that accumulates on the fan blades, causing an imbalanced, noisy fan.  For information on how to prevent this, see:

Even the slightest bend or imbalance in an AC blade can cause your blade to scrape it’s casing, also known as a fan cage.  This will make for a very noisy air conditioner.  If your blade is damaged, it will need to be replaced.  Also spin the fan with your hand to ensure that it is moving smoothly.  If it is loose, tighten the center bolt with a wrench or an allen wrench.  If the sound you hear is squeaky, and you’ve tried everything else mentioned so far, then the bearings likely need some lubrication.  If you want, 444 HVAC lubricant is available at your local hardware store but is unnecessary.  Good old WD-40 lubricant will do just fine.  If the bearings are still making a loud sound or if the blade does not rotate smoothly, call your local HVAC technician and they can replace your bearings for you.

If you hear a grinding sound, call your HVAC technician as this is a sign of pending bearing failure.

Step 2 – Noisy Air Conditioner – Rattling from Exterior Condensing Unit or Packaged Unit

The most common cause of rattling is something being loose.  If you have isolated the noisy air conditioner to your condensing unit – the outdoor one – (or packaged unit) itself:

  1. Again start by turning the AC unit OFF with the CB, disconnect and with the thermostat.
  2. Then, check all exterior and internal panels.
  3. If loose, tighten them, but check the inside panels before the outside panels.  It is a rule of thumb to work from the inside out when tightening your AC unit’s panels.

Step 3 – Why is My Air Conditioner So Loud?  Examining Rattling AC Ducts

This will require you to go into the attic.

Fixing a noisy AC - support joistsAgain, if you are not experienced with this, ensure to only walk on support joists (the wooden pieces between insulation).  See the pic on the right.  Again, unless you are experienced, I’d recommend calling your local HVAC contractor.

Check all of your ducts for loose joints and tighten them with duct screws and HVAC tape as necessary.  How?  Just use common sense and seal leaks.  Try not to overthink it.  If the rattling continues, you may have to call your HVAC contractor as the ducting currently installed may not be the proper size.

Step 4 – Ask What Kind of Sound is My Noisy AC Making?

Again, before you can answer the question “why is my air conditioner so loud,” always start by figuring out where the sound is coming from – you can’t diagnose a problem if you don’t know where the problem is to begin with!

Once you have localized the problem, another way of diagnosing it is to listen to the sound it is making.  Again, this is easier for an experienced HVAC technician, but here are a few general guidelines:

Listen to your ears – seems simple enough but the more harsh a sound is, the more likely it is to be serious.  If it hurts your ears, it’s time to turn it off and call a pro.

  • Mild Squeaking from Air Conditioner – Likely not serious – a bearing in need of lubricant or a dirty fan blade that is out of balance.
  • Rattling from AC or Duct – Again, not very serious – likely a loose panel in need of tightening, or a loose AC duct.
  • Grinding Noise – More serious – a bearing is likely going to fail, and if not replaced soon, it could damage other parts of your HVAC unit.
  • Hissing Sounds – Usually the most serious – if it is coming from your air conditioning unit, the most likely cause is leaking Freon (Also see, What is Freon?).  Don’t freak out though, unless you are certain that it is coming from your air conditioner itself – hissing could also be loose ductwork, which is not that serious.  When in doubt, give your local HVAC contractor a call.

Save Money on Your New Air Conditioner or Furnace

Hopefully we were able to successfully troubleshoot your noisy AC unit.  But if we weren’t make sure that you know the facts before purchasing a new one.  This short video will show you how to save money, and avoid the scams of predatory contractors.  Don’t overpay for your new AC:

TELL ME MORE ABOUT IT

If it is time to get a new air conditioner, also take a look at:

If you don’t live in our area (or don’t like us), here are some tips on how to choose a licensed HVAC contractor that will ensure your job is done right:

If you want to take care of your air conditioner for years of future use, try:

Final Thoughts on a Noisy Air Conditioner

So, why is my air conditioner so loud?  The answer to a noisy air conditioner just isn’t that simple.  But in the end, there are always some things that you can do yourself, so don’t be afraid to get your hands dirty.  Sometimes if your attempts haven’t worked out, it is just time to call in the pros.  For questions on who to call in your area for AC service and advice, ASM HVAC services Santa Clarita and all of the Greater Los Angeles area – click below to see if you’re in our area:

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