Air Conditioner Makes Loud Noise When Starting

image of homeowner covering ears due to air conditioner noises

It is not uncommon for machines to produce sounds. Even in our homes, with fans, refrigerators, washing machines, and dishwashers running, there is often some background noise. Similarly, air conditioners may emit a slight sound. However, it is not a typical occurrence if an air conditioner produces a loud noise, especially during start-up. If you hear any unusual sounds, investigate the source because it may indicate a more significant problem with the air conditioning unit. This article explores the reasons for and potential solutions to an air conditioner makes loud noise when starting.

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Air Conditioner Makes Loud Noise When Starting

At the start of the air conditioning cycle, homeowners may frequently hear loud sounds. Pay really close attention to the type of noise because each may indicate a distinct issue that requires attention. Do not attempt to fix the problem on your own. Seek the assistance of an HVAC technician instead.

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Types & Causes of Air Conditioner Noises 

Clanging & Banging

The outdoor unit of the AC has a blower motor that circulates air into the home. If this component becomes damaged, it can produce unusual sounds. Certain parts may also shift out of place and collide with the cage, leading to noise. Fallen debris, thermal expansion, and damper movement are also potential culprits.

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Screeching Noise

If you hear a grinding noise that resembles metal rubbing against metal, the fan motor bearings may have broken down. Although it is not urgent, it is best to resolve the issue promptly to avoid further damage. Before using the air conditioner, schedule an appointment with an HVAC technician to resolve the problem.

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Clicking Noise

image of an air conditioner compressor

Clicking noises may indicate electrical problems. When you try to turn on the air conditioner, the unit may not start. This issue should be addressed by experienced HVAC contractors who can investigate and address the underlying causes. Capacitors, compressors, and thermostats require special attention in this situation.

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Pulsating Sound

A gentle pulsating sound is normal as air moves through the system. However, if you can hear pulsating noise from the outdoor unit indoors, it may indicate an issue, such as twigs or broken fan blades lodged in the unit.

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Whirring Sound

This sound indicates a mechanical problem with the air conditioning unit, which can arise from both the indoor and outdoor components. Faulty belts, blades, bearings, and blown fan motors are common culprits. If you hear this sound, immediately turn off the unit and contact an air conditioner repair technician.

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Buzzing or Humming Noise

air conditioner compressor fans

If you hear a noticeable humming sound from the outdoor air conditioning unit, it may be due to debris lodged inside. Flowers, leaves, and branches can penetrate through the openings, so removing any foreign material should be a priority. Buzzing sounds may also indicate a malfunctioning fan.

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Rattling Noise

Rattling sounds in an air conditioning unit often occur when its parts become loose due to continuous vibration. Examine the screws and bolts around the unit and tighten them if necessary. Afterward, clean the coils and replace the air filter. However, calling an HVAC company and scheduling annual air conditioner maintenance may be best to avoid future issues.

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Common HVAC Contractor Fixes for Loud Air Conditioning Units

Clean & Straighten Coil Fins

Keep the coil fins clean to optimize the performance and efficiency of your air conditioning unit. You can achieve this by scheduling an annual air conditioner tune-up with an HVAC contractor. During this appointment, the contractor can use a fin comb to straighten the coil fins and a vacuum with a brush extension to eliminate any debris around the area.

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Tighten Loose Screws

Due to the numerous moving parts, it is expected that an air conditioning unit will vibrate during operation. This constant vibration may eventually cause screws to loosen over time, leading to audible rattling during operation. Schedule routine HVAC maintenance that includes tightening all screws to prevent this issue.

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Remove Debris in the Blades

To gain a better view inside the air conditioning cabinet, it is necessary to open it up. If you notice any debris inside, remove them immediately. Be especially careful to inspect the area around the fan blades for any foreign objects. This is a simple job that anyone can perform.

Straighten Bent Blades

Once you have removed dirt and debris from the air conditioning unit, inspect the blades for any issues. If you notice any unevenness, call a professional to bend them back into shape. An experienced HVAC contractor can perform this task with care to prevent any further damage. The contractor will inspect each blade thoroughly to ensure everything is in order.

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Lubricate the Motor

Screeching sounds from the air conditioning unit can indicate poor motor lubrication. Regular lubrication during tune-up services can prevent this issue from occurring. During these services, HVAC technicians use the appropriate oil to eliminate the noise and add oil to the oil ports near the bottom of the fan motor. Schedule an annual tune-up to avoid such issues.

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

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  • Inspect the Unit & Check the Condenser Fan – Start by examining the condenser fan located in the center of the outdoor unit. If it is movable, observe how the blades are rotating. If you notice any indications of imbalance or unexpected contact, it could be due to debris in the casing. Also, inspect the refrigerant piping and coils. If you are unsure of what to look for, it is best to skip this step and seek help from a professional.
  • Change the Air Filters – Regularly checking and replacing air filters is crucial to make sure the air conditioning unit runs efficiently. Clogged filters with dirt can impede airflow and cause the system to struggle, leading to a humming noise. You should make it a habit to inspect air filters at least once a month and replace them as needed.
  • Clean the Outdoor AC Unit – Always turn off the air conditioner before cleaning its outdoor unit to avoid accidents. Debris, such as dirt or leaves, may enter the unit through the openings, affecting its performance. Remove the top grille and clear any fallen objects inside. Once done, close the grille securely.
  • Check the Run Capacitor – Once you have finished cleaning the unit, turn the air conditioner on again and check if the fan is now rotating. If it is not moving, try jumpstarting it using a long stick to push the blades and create momentum. If the blades spin, this could indicate a faulty run capacitor.
  • Inspect the Indoor Air Handler – If you have finished checking the outdoor unit and it is not the source of the problem, turn your attention to the indoor air handler. Look for any ice build-up or bent coil fins. Turn off the power to allow the unit to thaw and dry out before switching it back on.
  • Call a Reliable HVAC Company – There are several steps or measures you can take to prevent air conditioner problems and address common noise issues. However, there are certain limitations to what untrained individuals can accomplish. If the noise persists despite following the suggestions on this list, seek the assistance of an HVAC professional.

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Preventive Measures for Air Conditioner Starting Problems

  • Use a Noise-Reducing Barrier – Consider installing a noise-reducing barrier to minimize air conditioner noise that can disrupt your daily routine and sleep patterns. Options like sound blankets or fences can effectively reduce noise levels, but consulting with an HVAC contractor before installation is essential to ensure proper placement and effectiveness.
  • Regular HVAC Maintenance – Schedule annual maintenance for your unit to prevent air conditioner noise and ensure proper functionality. Trained HVAC technicians can easily spot and resolve problems at the earliest stages, preventing them from worsening. They will thoroughly clean the unit, alleviating the need for DIY cleaning. This proactive approach significantly reduces the possibility of loud AC noise ever developing.
  • Call an HVAC Expert – If you notice any strange noises from your air conditioner, contact an HVAC contractor immediately. Ignoring the issue could lead to more severe problems down the line, which could be more expensive to fix. Addressing minor cooling system issues early on is always the most cost-effective approach.
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Observing your air conditioner can help you identify if something is wrong. Manufacturers try to minimize noise, so if you notice any unusual sounds, investigate as soon as possible. Pay attention to your AC and learn what is normal for it. If you suspect an issue, seek help from a competent professional technician for advanced repairs.

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