Picture of a Typical Window Air Conditioner, Front View, Cool Side.

How to Quiet a Noisy Window Air Conditioner

Anyone living in warmer climates and seeking to cool their bedrooms, living rooms, and other small to medium-sized living spaces, has probably grappled  with the problem of how to quiet a noisy window air conditioner.  Indeed, we’ve installed units from five to twelve thousand BTUs in our windows at various apartments, homes, trailers, and basements, and have been frustrated by all the noises of the roaring fans, cycling compressors, snapping air cleaners within, whistling vens, and the window rattling as the installation loosens. Here, we give our how-to instructions and hints for quieting those pesky, noisy window air conditioners.

Room units often thump, click, squeak, squeal, hum, whine, roar, and whir as their internal and external fans circulate the air around. e. buzz, and vibrate. Then, when the thermostat turns them off, these unit thumping noises, as the compressor shuts down.

Air conditioners, installed in a free window, work well for adding more cooling the primary HVAC system in the home, if it has one. They’re cheap to buy (if not to run).  Plus, you can move them from room to room as easily as people flit about. But quieting noisy window air conditioners you might have to do as they age.  Even the best ones grower noisier over time.

Also, window AC units come in a wide range of cooling sizes.  In fact, the larger units even accept 220 volt power for best performance.  But they have their drawbacks as well; their loud operation being perhaps the most irritating.

How to Quiet a Noisy Window Air Conditioner: Warnings and Cautions

Turn Power Off

Before working inside an air conditioner, be sure to disconnect it from mains power.  Otherwise, fatal electric shock can result, especially in 220-volt units.

Watch your Fingers  !

When working on the unit while it is operating is necessary, avoid spinning fan blades.  These can pack enough force to seriously hurt a finger or hand that gets in their way.

Picture of the rear view of a typical window air conditioner, its hot side.
Typical Window Air Conditioner, Back View, Hot Side.

How to Quiet a Noisy Window Air Conditioner: Tools & Supplies Needed

Screwdrivers and Nut Drivers

Have several sizes of each of the straight / blade, Philips, and star head drivers.

Allen Head Tools

You never know what kinds of fasteners you’ll need to tighten up in the numerous brands of window air conditioners out there. Some of them use larger Allen head screws to secure parts inside the case.

Universal Socket Set

We suggest the   Husky 16-Piece Universal Socket Wrench Set, Model 702200.  This comes with a handy holder to keep the wrench and sockets organized, and features most of the common socket sizes that are most useful during typical window air conditioner repairs.  You may also need a socket extender to reach those distant nuts and bolts.  But we’ve found this set to work well in about all circumstances we’ve encountered.  A socket set that has many chucks is very useful when working on quieting a noisy window air conditioner.

Multi Meter

Needed to check for correct line voltage and troubleshoot thermostats, micro switches, and fan motor windings.  But you need not spend a lot for one, as you don’t need great reading precision when testing air conditioner parts.  We suggest spending no more than $50 for a meter used in HVAC repairs.  You’ll get the precision you need, without having to worry too much over breaking a more expensive meter if you drop it.

HVAC Pressure Meter

In certain situations, the refrigerant pressure may be wrong.  This can cause noisy compressor operation.  But unless you plan on quieting lots of loud air conditioners, buying this tool is not necessary.  Only get one  if you’ve tried everything else to quiet things down, but the compressor still seems noisy.

White Lithium Spray Grease

Choose a product that has a very long straw, for reaching those recessed motor bearings within the fan. When quieting down noisy window air conditioners, you need an applicator that reaches all places inside the unit.

Rubberized Weather Stripping

Used to fill in spaces where metal vibrating against other metal can be a big noise source.  You can “plug up” this source of noise, by stuffing small pieces of this material in between the rattling metal pieces.

How to Quiet a Noisy Window Air Conditioner: Hints, Tips, Procedures, and Advice

Here are a couple of the tricks we’ve tried with moderate success, to   fix  or  reduce window air conditioner noise.

Install a High Quality Air Conditioner the Right Way

Unless you’ve bought a very well constructed and extra quiet window cooling unit, and took the pains to install it in accordance with low noise practices, air conditioners in general, and especially those designed to sit in a window, are inherently loud. Why?

Most units feature at least two motors (one for the indoor and outdoor fans, and the other is the refrigerant compressor).  Plus, some of the high end models also feature water pumps (to draw out the condensed water), electronic air cleaners (for keeping dust, pollen, and other allergens at bay).  One great way to eliminate the need for ever quieting noisy window air conditioners, is to spend a little extra money for a unit designed with quiet in mind.

Check for Correct Line Voltage

AC motors such as those found in common air conditioners, can hum and buzz excessively when the mains voltage is too low. When checking window air conditioners, addressing any low line voltage conditions is quite important.  Not only can the right voltage quiet most air conditioner hum, but likely prevents motor burnouts too.

To see if your voltage is too low, read the voltage at the outlet with a multi meter.  If too far below 110 or 220 volts, you may have other appliances on the same circuit, which can lower the value.  In that case, put the window air conditioner on its own circuit. We suggest to always put an air conditioner on its own circuit.

If the AC voltage is still too low, tell your utility company.  They may be able to help.  However, often the best approach is to find an air conditioner that runs well on 90 to 105 volts.

Be Sure Supporting Wall is Solid

If the wall in which the window air conditioner vibrates too much or is too wobbly, it may not be solid enough to give enough solid support.  Check this by knocking on the wall.  If even the gentlest of knocks sounds very loud or reverberates, the wall may actually amplify the AC sounds.  So you won’t gain much quieter ground for your window air conditioner if your wall is rickety and weak.

To solve this, choose either brick or cement walls for your window AC unit. Or, pick walls that offer thick wooden bases at window bottoms.  Also, blowing cellulose insulation inside the wall may dampen vibrations.  But the best answer to quiet this type of air conditioner noise is to move it to a more massive wall.

Grease All Brackets and Joints

Oil or grease any places where different pieces of metal in the air conditioner’s casing meet and could rub and bind. Use a thick oil or grease that can withstand heat, cold, and water without drying out, becoming too thin, or otherwise breaking down. One lubricant we used was white lithium grease.  And, we got great results with it.

Unfortunately though, no oil or grease will do the job forever.  Grease needs periodic re-application. Typically, we’ve “re lubed” our air conditioners every other year.

Oil the Fan Bearings

Fans with dry bearings can squeal, start up too slowly, and overheat and burn out.  So routine oiling with a long-tubed applicator helps them rotate more smoothly and quietly.  Oiling can also extend their lives considerably too.

But today’s bearings are pre-lubed. So they normally do not need more oil later.  In our experience, when they start squealing and squawking, oiling them solves the noise problem only briefly.  If they start squeaking too soon, you’ll probably have to replace the fan motor. Or at the very least, the bearing assemblies.

Clean and Vacuum Inside the Window Air Conditioner

Assure that none of the fan blades, louvers, vents, or air channels are caked with dirt and grime.  These deposits can make louder air flow noise through them.  Indeed, how to quiet a noisy window air conditioner often involves a good and deep cleaning of the unit, both inside and out.

Clogged airways can also whistle, roar, reduce cooling efficiency, and shorten air conditioner life.  So, keep the unit clean, for continued quietest operation.  For stubborn dirt, use a steamer, but avoid aiming the jet at electrical components inside, such as fan motor windings, starter capacitors, and switches.  Avoid shooting the steam near any wiring or plastic parts.

Tighten All Screws to Quiet a Noisy Window Air Conditioner

One very easy step to take, is to tighten all screws, tap down rivets, and re drive nails.  Indeed, screws and fasteners that secure the air conditioner to the window frame may loosen and thus squeak when vibrating during normal operation.  Preferably, you drive screws into the thickest, most sound and solid areas of the window sash.  This provides a more rigid backing that does not transmit sound as much.  Do not over tighten though, as you could strip the fasteners or crack the window frame.

Reinforce All Brackets and Joints

If seating the existing screws better in the last step does not help enough, then consider adding your own fasteners.  We’ve done this successfully.

Hoping to reduce the need for the lubricants mentioned above, we’ve reinforced the metal stand-off brackets in some of our window air conditioners.  These hold the fans and compressor in place. Plus, they suspend the fan motors and position the blades at the correct spot in front of the condenser coils.

Loose mounting that you find often causes tapping, pinging, and rattling due to motor vibrations shaking the loose pieces of adjoining metals.  So we drilled a single hole at the bases of each bracket where, it meets the surrounding case.  Then we drove a sheet metal screw into each one. As a final securing measure, we used thread lock on the screws to ensure their continued tightness.  This step showed the greatest noise-reducing effect.

While some vibration is still heard, the motors and mounting parts got much quieter.  Thus, we keep a good supply of these fasteners around just for addressing these sorts of noise problems.

Replace Noise Isolating Grommets and Washers on the Compressor

The compressor inside is the largest source for the low-frequency hums, growls, and raspy vibrations.  These seem to carry all through the house where window air conditioners are running.  So, manufacturers often suspend the compressor, atop these flexible washers

This compressor vibration problem may not be as easy as easy to solve as the air noises, squeals, and bangs. But we reduced hum by assuring that these vibration absorbing washers have not rotted or dried out. When properly fastened, the bracket should hold the compressor firmly, but not tightly. In most window air conditioners, the compressor should “rock” a little due to the springiness in the flexible washers upon which it sits.  But you may not get enough cushioning when these soft washers rot or fall out.

Replace any Frayed or Loose Belts

Rubber fabric belts are often found in window air conditioners.  These transfer motion from the motor to the fan blades.  But failing belts here can cause excess hissing, rubbing and squealing sounds, and thus, can add markedly to the loud noise your AC unit makes.

Replace the Window Air Conditioner

Sadly, the cheaper window units are inherently noisier. So they may not be suitable for bedrooms or other areas where you want near whisper quietness. Sometimes, especially in older cooling units, there’s just no toning them down. Thus, your best bet is to just replace them.

We’ve found that replacing these loud appliances with higher quality, newer models designed for quieter running, is usually the least aggravating yet most effective solution.   But when that’s not an option, the above steps and tips have proven to work well; not perfect, mind you, but effective.   We’ve seen them work well in homes, apartments, trailers, and high rises. Hopefully, they’ll work for you too.  Good luck.

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References for How to Quiet a Noisy Window Air Conditioner

  1. What are air conditioners?    on Wikipedia
  2. Where to buy   Window Air Conditioners

Revision History

  • 2020-05-22: First published.