Fixing Noisy Window Air Conditioner Unit Tips




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.



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.

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

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 economical to purchase (if not to operate), can be moved from room to room as easily as people move around, and come in a wide range of cooling capacities; 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.

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).

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

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, as these can pack enough force to seriously injure a finger or hand that gets in their way.

Tools & Supplies Required

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.

Socket set.  We recommend 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.

Multimeter.  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.

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.

Repairing Noisy Window Air Conditioner 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.

Verify 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.  Read the voltage at the outlet with a multimeter.  If too low, 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, inform your utility company, who 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 adequately support an operating air conditioning unit.  Verify by knocking on the wall with a knuckle.  If even the gentlest of knocks sounds very loud or reverberates, the wall may actually intensify and strengthen the compressor sounds.  Choose either brick or cement walls, or walls that provided thick wooden bases at the window bottoms.  Blowing cellulose insulation into interior wall cavities may reduce vibrations.  But the best answer to correct this type of noise is likely to relocate the air conditioner to a harder, more massive wall.

Lubricate   all brackets, joints, rivets and 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. We’ve used white lithium grease with impressive results. 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.  It can extend their lives considerably as well.  However, today’s bearings are pre-lubed and do not normally require additional oil later.  In our experience, when they start squealing and squawking, oiling them solves the noise problem only temporarily.  If they start squeaking too soon, you’ll probably have to replace the motor, or at the very least, the entire bearing assemblies.

Clean and vacuum inside the unit.  Assure that none of the fan blades, louvers, vents, or air channels are caked with dirt and grime, as this can intensify the air flow noise through them.  Clogged air passages can also result in whistling, reduced cooling efficiency, and shorter unit 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.

Tighten existing screws   that secure the air conditioner to the window frame.  Preferably, the screws should be driven into the thickest, most sound and solid areas of the window sash, to provide a more rigid, less vibration transmitting backing.  Do not over tighten, 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, that hold the fans and compressor in place. These brackets suspend the fan motors and position the blades at the correct spot in front of the condenser coils. Loose mounting here can cause tapping, pinging, and rattling as vibrations from the motors rattles the loose pieces of adjoining metals.  So we drilled a single hole at the bases of each bracket where, it meets the surrounding case, and 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 internal motors and mounting parts are far quieter than before the sheet metal screws were applied.

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 that seem to carry all through the house where window air conditioners are operating.  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 hum has been minimized by assuring that these vibration absorbing washers have not deteriorated is secure in the brackets mentioned above. 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.



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 that replacing noisy room air conditioners with higher quality, newer models that are designed specifically to emit less noise, is usually the least aggravation 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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References

Revision History

  • 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.