Common Types of Air Conditioner Noises

Maybe you are sleeping and a sound shriek wakes you up. You might be watching television when a whirring screech disrupts your fun. Or it might just be a slight change in how your air conditioner sounds. Strange sounds from your air conditioning system range from minor issues like a dirty air filter to major components on the cusp of failure.

Redman Services, your Home Service Hero, helps you decipher normal air conditioner noises from sounds that could cost you hundreds of dollars. When you respond properly to loud noises with air conditioner repair, you can help prevent a disaster. There’s nothing worse than losing your cooling system in the heat of summer. Let us help you better protect your home against extreme and expensive repairs.

What are Normal AC Noises?

Your air conditioning system is complex with lots of moving parts. Both the air conditioning unit, indoor air handler and air ducts all contribute to your air conditioner making noise during operation. Some of these noises are normal and nothing to worry about, while others can indicate a problem. Knowing what is normal and what isn’t can help you determine if it’s time to call in a professional.

  1. Humming: The motor in your air conditioning unit emits a constant humming noise. The outdoor unit will maintain a consistent sound with very little variation.
  2. Blowing: The sound of air moving through the vents is another normal noise that should be consistent. When the indoor blower fan is running, air ducts are clean and vents are properly adjusted a steady whooshing or whistling sound is normal.
  3. Clicking: The electrical components switching on may be accompanied by a clicking sound. The expansion and contraction of metal parts may also cause a click, so an occasional click is normal.
  4. Gurgling: When condensate builds up in your system, this liquid is directed from your AC unit via a drain line. Liquid gurgling when your system is not operating may be the condensate line draining.

These normal sounds should not be ignored, though. Instead, you should pay attention to these sounds and become accustomed to the sounds your air conditioner is making. A new unit may sound different than your older air conditioner. For new homeowners, it can take time to become comfortable with the sounds of a different air conditioner.

What Kind of Noise Is an Air Conditioner Hum Associated With?

The most common sound of an air conditioner unit is a steady hum during operation. An air conditioner unit hum is usually associated with the operation of the motor and fan. When the air conditioner is turned on, the motor starts running, and this generates a constant, low-level hum.

The hum should be a consistent, even noise that doesn’t change in volume or pitch. If the hum becomes louder or changes in any way, it may indicate a problem with the motor, loose hardware, dirty fan/fins or another part of the air conditioner. Quickly responding to any change in sound, especially from your air conditioner unit is important. Often a professional can diagnose the issue, address it with simple maintenance and protect your air conditioner against breakdown.

What is the Most Common Source of Abnormal Noises in an Air Conditioner?

The most common source of abnormal noises in an air conditioner is loose hardware, dirty components or damaged parts. There are many moving parts within your air conditioner, such as the fan blade that may come loose from its mounting. Loose connections and damaged parts cause buzzing, rattling, or clanging sounds.

Another common source of abnormal noises is a malfunctioning fan motor and other electronic components, which can produce a squealing or grinding sound. In both cases, it is important to have the issue addressed promptly by a professional to prevent further damage to the air conditioner and to ensure that it continues to operate efficiently.

8 Strange Air Conditioner Noises and What They Could Mean

  1. Squealing: High-speed moving parts may emit a high-pitched squealing noise. A fan motor, bearings and belts that are loose or worn out may first sound like a squeal. If you hear these air conditioning noises, shut down the system. A squealing noise inside the air handler can cause this type of issue. The blower wheel and belts can make a squealing noise under stress. These are usually loud noises and – if left ignored – can break and damage other components. Sometimes a squealing noise is just loose or broken hardware that can easily be replaced with an affordable air conditioner repair.
  2. Grinding: Other common types of air conditioner noises include grinding. When sealed bearings wear down, the resulting friction will present as a grinding noise. Bearings may be an affordable air conditioner repair, but the components they are designed to protect can be expensive. If your air conditioner is making a grinding noise, turn off the system and let a professional technician fix the issue. On rare occasions, a build-up of dirt, debris and other foreign bodies can create grinding noises inside air conditioners. Professional technicians make quick work to diagnose and get your air conditioner running smoothly.
  3. Buzzing: When parts are loose, buzzing sounds are a common noise. The issue could be in the air conditioner or within the air handler. A buzzing noise indicates that something is loose like hardware or the fan blade. Loose parts can cause damage to other components and reduce the efficiency of the AC, so it’s important to turn off your air conditioner immediately from the thermostat.
  4. Rattling: A rattling noise is most commonly indicative of loose hardware or foreign objects. Since hardware holds components in place, if you hear a rattling noise in your air conditioner, schedule an inspection as soon as possible. Loose parts can cause damage to other components and reduce the efficiency of your air conditioner.
  5. Clanging: A loud clanging noise can indicate that something has come loose either inside the AC unit, air handler or even an external panel. Time and weathering can cause bolts and other hardware to strip or come loose. You might examine the panels if you hear clanging. Air conditioners have panels to protect components and keep dirt and debris from entering the HVAC system. This AC noise should always be examined promptly. If you cannot identify loose panels yourself, call on our team to repair your air conditioner.
  6. Hissing: A hissing sound can indicate a leak in the refrigerant line. Pressurized refrigerant may range from hissing to even bubbling sounds if a line is cracked or a connection is worn. Hissing sounds from refrigerant lines may be heard even when the system is shut down. Leaks can be dangerous, and at the very least, lead to decreased efficiency and increased energy costs. A professional should be called to diagnose the issue and make repairs as needed.
  7. Thumping: A thumping noise can indicate that the fan blades are out of balance. If you have not maintained your air conditioner, dirt on fan blades can cause this loud noise. This will only occur when air conditioners are in the cooling cycle. This can cause vibrations and increase the wear and tear on the unit including damaging the motor.
  8. Banging: A loud banging noise can indicate that the fan blades have come into contact with an object, such as a leaf or a piece of debris. Within the air handler, foreign objects or a damaged air filter can lead to banging noises. This can cause significant damage to the fan blades and the air handler, so it’s important to have the issue addressed promptly. It is best to shut down your system when you hear these strange noises.

Whether strange noises are coming from the indoor unit or the outdoor air conditioner, you should always act promptly. When you react to rattling noises, high-pitched squealing noises, loud buzzing noises or hear loud noises of any kind, an HVAC professional may be able to prevent a breakdown without performing a major repair.

What are the Parts of An Air Conditioner?

The major moving parts of your air conditioner can be expensive to replace so when you are alert to the common types of air conditioner noises, you can protect these components. The major moving components of air conditioners include:

  1. Compressor: The compressor is the heart of the air conditioning system. It is responsible for compressing and circulating refrigerant through the system. The compressor is a mechanical pump that moves the refrigerant from the evaporator to the outdoor condenser unit. Most critically, the compressor is responsible for the high internal pressure necessary for the refrigerant to cool air.
  2. Blower Wheel: The blower wheel is located inside the air handler. Otherwise known as the blower fan, it is responsible for circulating air throughout the system. The blower fan has vanes that spin as air is drawn through it, providing a consistent current throughout your home. Dirty air filters, clogged air ducts and improper ventilation can cause the blower fan to make strange noises. The blower fan belt drives the wheel from the motor. Many noises within the air handler are related to these three components.
  3. Blower Motor: The electric motor works with the blower fan. Faulty electrical signals and a malfunctioning thermostat may result in wear, sounds and eventual failure. Regular maintenance prevents most motors from breaking down or seizing.

What Other Components Can Make Strange Sounds in an AC System?

In addition to the blower wheel, motor and compressor, other components of your air conditioning system can make strange sounds. If the steady humming sound of your outdoor unit is disrupted, maintenance is highly recommended. There are a number of minor components that result in AC noises.

  1. Evaporator coils: If the evaporator coils are dirty or clogged, they can make a hissing or gurgling sound as the refrigerant flows through the coils. Cracks in the evaporator coils can lead to whistling noises.
  2. Refrigerant line: That whistling from the evaporator coil or refrigerant line is likely a refrigerant leak. These will always cause your system to be less efficient and energy bills to increase. If there is a problem with the refrigerant line, such as a leak or restriction, the air conditioning system can make a hissing sound during the cooling cycle.
  3. Expansion valve: The expansion valve is responsible for regulating the flow of refrigerant into the evaporator coils. If the valve becomes clogged or fails, it can cause the AC system to make a clicking or ticking sound.
  4. Outdoor fan: The outdoor fan helps to dissipate heat from the condenser coils. If the fan blades are dirty, damaged or worn, they can cause the AC system to make a rattling or clanging sound. The fan motor can also make a clicking noise or a buzzing sound due to faulty electrical signals, bad connections and worn hardware.
  5. Condenser coils: The condenser coils help to dissipate heat from the refrigerant. A dirty, cracked or clogged coil in the air conditioner will make a hissing noise or gurgling sound.
  6. Air Ducts: Air ducts can become damaged and leak. Some designs of air ducts are more efficient and quiet than others. A large amount of energy waste is lost through broken seals and damaged air ducts. A whooshing, whistling or strange humming noise may be an air duct issue. Another sign that won’t make much of a sound is weak airflow through one or more vents.

When you hear any of the common types of air conditioner noises that warn of issues, call on your Home Service Hero at Redman Services. As a local company, we provide complete air conditioning system repairs and maintenance. In fact, most homeowners are delighted to find our affordable air conditioner tune-ups catch many of the causes of AC noise before they occur.

What is the Best Time to Schedule Maintenance and Repairs of AC Units?

After the winter, your outdoor unit is dirty from winter weather. Even when you use a cover, changes in temperature and accumulation of snow atop your unit are invitations for trouble. Your HVAC system is one of the most important and complex appliances in your home. To avoid waking to a shrieking noise or sweltering heat because your air conditioner has failed in the summer, schedule a routine maintenance service each spring with your local HVAC professionals.

When you perform preventative air conditioner maintenance in the spring, prior to your system starting for the season, you help to improve efficiency, protect against repairs and prolong the service life of your air conditioner. Contact Redman Services today for all of your home’s cooling needs.


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