Now, About That Noise Your Air Conditioner's Making...

Wondering about the noise your air conditioner's making? You should be. When an air conditioner makes an unusual noise, more often than not it's a signal that there is a much bigger problem happening inside of the air conditioning system.

Most air conditioner noises stem from either the ductwork, air handler or outdoor compressor unit. The tips below will help you to diagnose a noise your air conditioner's making,  but you should leave rectifying the problem to the professionals, as they will have the expertise to pinpoint the origin of the problem and fix it.

Further, leaving an air conditioner noise unchecked could lead to significant problems down the line, as noises are generally an indication that your system needs expert attention, whether the problem is big or small.

Air handler

The following noises your air conditioner can make may signal that your indoor air handler/evaporator unit is faulty:

  • A bad compressor will make a banging or clanking noise.
  • Leaky refrigerant lines generally create a hissing or bubbling sound.
  • However, buzzing can also indicate that the unit's electrical components are wearing out, such as the relay switch on the compressor, electrical connections or circuit breakers.
  • The controls and relays on the condenser or compressor will create a clicking noise at the air handler. For instance, a bad thermostat will cause the relays to come on and off repetitively, making a clicking sound.
  • If you hear noises when the air handler starts up, such as a clanking, rumbling, or rattling sound, the compressor or condenser may have hardware that has become loose.

As you can see, however, noises your air conditioner's making may seem as if they stem from the air handler, when they originate elsewhere. That's why professional help is a must.


Noises that seem to be coming from the ductwork could be a sign that there are problems with the actual ducts themselves, or the ducts could be conducting a noise that stems from an A/C component. Here's what to listen for:

  • Contracting ductwork often makes noises akin to clanking, hissing, roaring or whistling, as the metal in duct-pipe materials expands and contracts as conditioned air moves through it.
  • When animals become trapped in the ducts, you may here fluttering noises (birds), scratching noises (squirrels or rats) or buzzing noises (wasps or bees).
  • A rattling, squealing or squeaking noise your air conditioner's making often stems from a bad blower or fan.
  • Leaks in the supply or return portions of the air duct system can also cause noises, such as whistling or hissing.
  • A vibration damper that is off kilter or doesn't fit properly will generally transmit noises through the ducts, such as a clanking, buzzing or rattling sound.
  • Several problems can occur in the air handler that will first make themselves known through unusual sounds, including an obstructed fan blade making a clicking or ticking sound, a loose pulley on the fan making a rattling sound, or bad bearings or poorly lubricated fan making a squeaking noise.

Outdoor A/C unit

The A/C unit outside of your home is called the condenser, and it also houses the compressor. It is prone to making these noises:

  • Clanking or banging noises signal a costly problem. These types of sounds indicate a loose connecting rod, crankshaft or possibly a piston pin. As this component is tightly sealed, the only option is generally to replace the entire unit.
  • Hissing or bubbling at the condenser signals a refrigerant leak.
  • A buzzing sound coming from the unit's motor could be coming from either a wire that is loose, a bad connection or a burned contactor.
  • Rattling or clanking most often stems from the compressor itself -- if it becomes loose.
  • Rattling, rumbling, or ticking noises upon start-up generally begin when hardware is loose, particularly if the rattle sounds like it's coming from metal materials.
  • Humming sounds often happen if the unit's motor doesn't start or it starts up slowly, which generally indicates that the capacitor should be replaced. However, if the unit doesn't start at all, it's also possible that the compressor motor has failed.
  • Screaming noises often indicate high internal pressure inside of the compressor -- a dangerous situation. In this case, shut the system down and call an HVAC technician immediately.

How to avoid the noise your air conditioner's making

One of the best ways to prevent any air conditioner problems is to have regular preventive maintenance performed. Along with cleaning the coils and lubricating necessary parts, service affords your cooling technician the opportunity to spot problems before they turn into larger, costlier ones. And you'll reduce the risk of having to endure the nuisance that the noise your air conditioner's making causes.

If you're tired of that noise your air conditioner's making, or you need to schedule a tune-up, give the experts at Jones-Rogers Inc. a call today. We have served homeowners in northern Virginia since 1970.

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