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

Fixing Noisy Window Air Conditioners, How To

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 noisy window air conditioners. Indeed, we’ve installed units from five to twelve thousand BTUs in our windows at various apartments, homes, trailers, and even basements, and have been frustrated by all the noises of the roaring fans, cycling compressors, snapping air cleaners within, and the window rattling as the installation loosens. Here, we give our how-to instructions for fixing 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 heaters make the similar noises, as their metal parts and the heating element itself shrink during cool-down.

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

Also, they come in a wide range of cooling capacities.  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 one.

Fixing Noisy Window Air Conditioners: 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, particularly in the 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. Fixing noisy window air conditioners.

Fixing Noisy Window Air Conditioners: 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 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 virtually all circumstances.  A socket set that has many chucks is very useful when fixing noisy window air conditioners.


Needed to  verify correct line voltage and troubleshoot thermostats, micro switches, and fan motor windings.  however, you need not spend an exorbitant amount, as great reading precision is not required when testing air conditioner components.  We recommend spending no more than $50 for a meter used in HVAC repairs.  You’ll get the precision you need for this work, without having to worry too much over breaking the meter if you drop it.

HVAC Pressure Meter

In certain situations, the refigerant pressure may be incorrect, and can cause noisy compressor operation.  However, unless you plan on quieting lots of loud air conditioners, buying this tool is not absolutely necessary.  Only procure it if you’ve tried everything else to quiet things down, but the compressor still seems noisy.

White Lithium Spray Grease

Choose a product that features a very long straw, for reaching those recessed motor bearings within the air cooler. When fixing noisy window air conditioners, you need an applicator that can reach all places inside the unit.

Rubberized Weather Stripping

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

Fixing Noisy Window Air Conditioners: Hints, Tips, Procedures, and Advice

Here are a couple of the tricks we’ve attempted with moderate success, to   fix  or  reduce the electric heater noise. Note that these procedures apply only to convection type electric baseboard heaters, as these tend to exhibit lower surface temperatures than the hotter, radiant units.  Do not use lubricants on or near any glowing-type heating elements found in radiant heat sources.

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 more extravagant 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 fixing 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 fixing noisy window air conditioners, addressing any low line voltage conditions is very important.  Not only can the right voltage quiet the air conditioner, but likely prevents motor burnouts as well.

To see if your voltage is too low, read the voltage at the outlet with a multimeter.  If too far below 110 or 220 volts, you may have other appliances on the same circuit, which can lower the value.  If so, put the window 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 in this situation, 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 cooling unit vibrates too much or is too wobbly, it may not be solid enough to give enough solid support to an operating air conditioner.  Verify by knocking on the wall with a knuckle.  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 when fixing noisy window air conditioners if your wall is rickety and weak.

To solve this issue, choose either brick or cement walls for your AC unit. Or, pick walls that offer thick wooden bases at window bottoms.  Also, blowing cellulose insulation into interior wall cavities may reduce vibrations.  But the best answer to fix 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 libricant we used will fixing noisy window air conditioners, was white lithium grease.  And, we got impressive results with it.

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

Oil Fan Bearings

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

However, 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, replace the entire 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 intensify air flow noise through them.  Indeed, fixing noisy window air conditioners often involves a good and deep cleaning of the AC unit, both inside and out.

Clogged air passages can also result in whistling, roar, reduced cooling efficiency, and shorter air conditioner life.  So, keep it 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

One very easy step in fixing noisy window air conditioners, 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 air conditioner operation.  Preferably, you drive screws into the thickest, most sound and solid areas of the window sash.  This provides a more rigid, less vibration transmitting backing.  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 previous step does not help enough, then consider adding your own fasteners.  We’ve done this successfully.

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

Loose mounting that you find while fixing noisy window air conditions 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 grew far quieter than before we applied the sheet metal screws.  We keep a good supply of these fasteners around just for fixing noisy window air conditioners.

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 operate.  So, manufacturers often suspend the compressor, atop these flexible washers

This compressor vibration problem wasn’t as easy to solve as the air noises, squeals, and bangs. But we reduced hum by assuring that these vibration absorbing washers have not deteriorated. When properly fastened, the bracket should hold the compressor firmly, but not tightly. In most room 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 adequate cushioning when these soft washers rot or fall out.

Replace any Frayed or Loose Belts

Rubber impregnated fabric belts are often found in air conditioners.  These transfer motion from an electric motor to the fan blade assembly.  However, failing belts here can create excess hissing, rubbing and squealing sounds, and thus, can contribute markedly to the over noise generated by your AC unit.

Replace the Window Air Conditioner

Sadly, the cheaper room units are inherently noisier, and so, may not be suitable for bedrooms or other areas requiring near whisper quietness. Sometimes, especially in older cooling units, there’s just no toning them down, and your best bet is to just replace them.

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

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Fixing Noisy Window Air Conditioner References

Revision History

  • 2019-02-17: Added more subheadings and tags.
  • 2019-01-02: Added subheadings.
  • 2017-01-25: Updated tags list.
  • 2015-12-22: Added appropriate tags.
  • 2015-07-05: Added pictures.
  • 2015-03-02: Added the “Tools & Supplies Required” section, and fixed some typos.
  • 2014-12-30: Originally published.