Air Conditioner Makes Loud Noise When Starting

image of homeowner covering ears due to air conditioner noises

Machines producing sounds are common. With the presence of fans, refrigerators, washing machines, and dishwashers running, homes are seldom completely silent. Even air conditioners emit a faint noise. However, it is not a regular function if an air conditioner produces a loud noise during its startup. It is crucial to investigate the source of any unusual noise and consider it a possible symptom of a more significant issue with the air conditioning unit. This article delves into some of the reasons for a loud air conditioner and provides potential solutions.

Explore Our Heating & Cooling System Services Call To Schedule A Free, In-Home Estimate

Air Conditioner Makes Loud Noise When Starting

It’s common for homeowners to experience loud noises during the air conditioner’s startup. Pay close attention since various types of sounds indicate distinct problems that require addressing. Attempting to resolve the issue independently is not recommended. Seek assistance from an HVAC technician whenever necessary.

Types Of AC Noises & Their Causes

image of an air conditioner condenser

Keep reading to explore more about unusual air conditioning noises.

Clanging & Banging

The outdoor unit of the AC houses a blower motor responsible for circulating air into the home. Any damage to the blower motor can result in unusual noises. Parts may shift from their original positions and collide with the cage. Possible causes of this damage include fallen debris, thermal expansion, and damper movement.

Call Today: (860) 399-6218

Clicking Sounds

If you hear clicking sounds when you try to start the air conditioner, it could indicate electrical problems. In case the unit fails to turn on, it is better to leave the matter to professional HVAC contractors. These experts will pay attention to critical components such as the capacitor, compressor, and thermostat.

Related Article: Major Consequences Of Not Replacing Your Home Air Filter

Screeching Noise

image of an air conditioner fan depicting a compressor fan not working

If you notice a grinding sound similar to metal rubbing against metal, the fan motor bearings may be damaged. While it is not urgent, it is wise to take precautions to avoid further damage. It is best to arrange for an HVAC technician to repair it before using the air conditioner.

Pulsating Sound

It is normal to hear a low-level pulsating sound when air flows through the system. However, it is not normal if you detect pulsating noise from the outdoor unit while inside. In such a scenario, the noise could indicate an issue, such as broken fan blades or twigs stuck in the unit.

Learn More About Our Home HVAC Services Call To Make An Appointment

Whirring Sound

This sound indicates a mechanical problem within the air conditioning system, originating from indoor or outdoor units. Possible culprits include damaged belts, defective blades, malfunctioning bearings, and blown fan motors. It is wise to switch off the unit without delay and seek the assistance of an air conditioner repair specialist.

Related Article: Advantages Vs. Disadvantages Of Washable HVAC Filters

Buzzing or Humming Sound

image of HVAC contractor performing air conditioner repair

If you hear a noticeable humming sound from your outdoor air conditioning unit, inspect it for any trapped debris. It is possible that leaves, flowers, or branches have made their way through the openings, so removing them is critical. The humming noise could signify that the fan is malfunctioning and may need to be replaced.

Get Started - Call To Schedule A Free Consultation

Rattling Sound

Frequent rattling from an air conditioner is typically caused by parts that have become loose due to prolonged vibration. To address this issue, inspect the screws and bolts surrounding the unit and promptly tighten any that appear loose. It is also wise to clean the coils and replace the air filter as a preventive measure. Consider scheduling annual air conditioner servicing with an HVAC company for optimal maintenance.

Related Article: What Does An Air Conditioner’s SEER Rating Actually Mean?

Common HVAC Contractor Fixes for Loud Air Conditioning Units

Clean & Straighten Coil Fins

To enhance the performance and efficiency of your coil fins, it is important to keep them clean. Schedule an annual air conditioner tune-up with an HVAC contractor who can use a fin comb to straighten the coil fins and a vacuum with a brush extension to remove all dirt and debris from the surrounding area.

Related Article: Why Is Smoke Coming Out Of The Vents When AC Is On?

Tighten Loose Screws

The air conditioner’s operation involves many moving components, which can result in vibrations during use. Over time, these vibrations may cause screws to become loose, leading to audible rattling sounds during operation. To prevent this, schedule regular HVAC maintenance that involves tightening all screws to ensure they remain secure.

Get Started - Call To Schedule A Free Consultation

Remove Debris in the Blades

Open the cabinet to obtain a better view of the air conditioning unit’s interior. If you notice any debris present, promptly remove it. Take extra care to inspect for any foreign objects near the fan blades. This task is straightforward and can be performed by anyone.

Related Article: How Does My Air Conditioner Cool My Home?

Straighten Bent Blades

air conditioner condenser fan closeup

Inspect the blades for any issues after cleaning off dirt and debris. If you notice any uneven blades, carefully bend them back into shape. If you observe significant bending or damage to the blades, it is best to call an HVAC contractor to handle the repair work to prevent further damage. They will meticulously go through each blade until everything is in proper order.

Learn More About Our Home HVAC Services Call To Make An Appointment

Lubricate Motor

If you hear screeching noises from your motor, it may indicate inadequate lubrication. To avoid this issue, it is best to perform a tune-up service that includes lubrication of the unit. During this service, the technician will use the appropriate oil to eliminate the noise and add oil to the oil ports near the fan motor’s base. Doing so can prevent screeching sounds from occurring in the first place.

Related Article: How To Find A Competent Air Conditioner Replacement Company 

What You Can Do If The Air Conditioner Produces A Loud Noise

Inspect the Unit and Check the Outdoor Fan 

Examine the condenser fan located in the middle of the outdoor unit. Verify that it can rotate and observe how the blades are spinning. If you detect any imbalance or sudden contact, it may be caused by debris in the casing. Also, inspect the coils and refrigerant piping. However, if you are unsure what you are looking at, skip this step and leave it to a professional.

Change Your HVAC Air Filters

removing dirty HVAC filter for home central air conditioning system

Homeowners should regularly check and replace their air filters. When the filters become clogged with dirt, the airflow is compromised, causing the unit to struggle and possibly emitting a humming noise. To ensure optimal performance of your air conditioner, make it a habit to inspect the air filters monthly and replace them as needed.

Clean Your Outdoor AC Unit

The outdoor AC unit is susceptible to the elements present in its surroundings. Dirt and debris can penetrate through the slits, affecting their performance. To ensure your safety, turn off the unit before opening the case. Remove any fallen objects by taking off the top grille. Once you are done, be sure to close the case securely.

Get Started - Call To Schedule A Free Consultation

Check the AC Run Capacitor

Once you have finished cleaning the unit, switch the air conditioner back on to check if the fan is rotating. If it still isn’t moving, try jumpstarting it using a long stick to push the blade and create momentum. If the blades start to spin, this indicates a malfunctioning run capacitor.

Related Article: What Can I Expect During My HVAC Installation?

Inspect Your Indoor AC Air Handler

On occasion, the issue may not lie with the exterior component. Once you have conducted your examination, proceed to the indoor air handler. Verify whether there is any accumulation of ice or any bent coil fins. Turn off the power to allow it to defrost and dry thoroughly before reactivating it.

Call a Professional HVAC Company

image of an hvac contractor using manometer to check ac refrigerant levels

There are various measures that homeowners can take to avoid air conditioner problems and resolve typical noise disturbances. However, untrained individuals have their limitations. If you have done all the actions on this list and can still hear the noise, contact an HVAC professional for assistance.

Preventive Measures for AC Starting Problems

  • Install Noise-Reducing Barrier – The noise emitted by an air conditioner can hinder your daily activities and disrupt your sleep patterns, causing difficulties in falling asleep. You can avoid this issue by installing a barrier that diminishes the noise. Consider utilizing a sound blanket or a noise-reducing fence for this purpose, but it is recommended to consult with an HVAC contractor before proceeding.
  • Schedule Regular HVAC Maintenance – Arrange for yearly maintenance of your air conditioner unit to ensure optimal functioning. Skilled technicians can identify potential issues in their initial stages and provide prompt solutions to avoid their escalation. They will also carry out comprehensive cleaning, saving you the trouble of doing it yourself. Regular maintenance decreases the likelihood of loud air conditioner noise ever emerging.
  • Call an HVAC Expert – contact an HVAC contractor as soon as you notice any unusual noise from your air conditioner. Ignoring such sounds can lead to the development of more serious issues. Addressing minor problems with your cooling system is always more cost-effective than dealing with major failures later. Prompt action is vital to avoid potential expenses.


Be attentive to your air conditioning system, as it can indicate if something is amiss, provided that you are willing to listen. Keep in mind that AC manufacturers make efforts to reduce noise. You can become familiar with what is typical by observing your air conditioner over a period of time. If you notice any anomalies, take action and investigate promptly. For complex repairs, seek assistance from a skilled and qualified technician.

Call Wilcox Energy Today Explore Our Case Studies

Call Wilcox Energy For All Of Your HVAC Requirements


At Wilcox Energy, we take pride in providing exceptional heating and cooling services to both residential and commercial clients throughout southern Connecticut. Our team comprises highly qualified technicians certified and equipped to perform outstanding HVAC tune-ups, repairs, installations, and replacements. We assure you that each of our technicians possesses the knowledge and experience necessary to handle your HVAC system proficiently.

We are dedicated to delivering the most competitive heating and cooling service rates in the locality. Our maintenance services aim to enhance your comfort and increase energy efficiency while reducing your home’s heating and cooling expenses. If you require an HVAC repair or replacement system, we will recommend the best option for your home, always staying within your budget. Our work is backed by a guarantee to ensure your complete satisfaction. To schedule an appointment, please contact Wilcox Energy today. We provide free, in-home estimates.

Call Now: (860) 399-6218 Read Our Reviews

For more information about our HVAC services, be sure to contact Wilcox Energy. You can click here to contact us, or you can call us at (860) 399-6218 to find out more. We offer a full line of heating and cooling repairs, maintenance services, and installations. Click the link to view our service area.