Understanding Why Your Air Conditioner Makes A Loud Noise When Starting

young girl covering ears depicting Air Conditioner making Loud Noise When Starting

Some noise from household appliances is normal. From the gentle hum of refrigerators to the rhythmic whoosh of dishwashers, these sounds are a familiar backdrop in any home. However, if your air conditioner starts with a jarring racket, it’s a clear sign that something isn’t right. Odd noises can be indicators of underlying issues that may require immediate attention. This article from Columbus Energies explores common causes and effective solutions for addressing why your home’s air conditioner makes loud noise when starting.

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Air Conditioner Starts with a Bang: Understanding the Noises

Residential air conditioner units depicting air conditioner making loud noise when starting

It’s common for homeowners to notice loud sounds as their air conditioner kicks into gear. Pay attention to the nature of these noises, as each type can signal a specific problem needing resolution. Attempting repairs yourself isn’t recommended; instead, enlist the expertise of a qualified HVAC technician.

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Different Air Conditioner Noises & Their Origins

Keep reading to learn more about the unusual noises your air conditioning unit might make.

Clanging & Banging AC Unit Noises

The blower motor in your AC’s outdoor unit circulates air throughout your home. When damaged, it can produce strange sounds. Components may shift and start striking the protective casing. Additionally, fallen debris, thermal expansion, and damper movements can also be contributing factors.

Screeching Air Conditioner

HVAC technician examining screeching air conditioner

A screeching noise often indicates worn fan motor bearings, suggesting metal is grinding against metal. While not urgent, it’s wise to have an HVAC technician address this to avoid further complications.

Clicking Air Conditioner

Clicking sounds usually signal electrical issues. If your air conditioner fails to start despite attempts, professional HVAC contractors should inspect critical components like the capacitor, compressor, and thermostat.

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Pulsating Noise from Cooling System

A subtle pulsating sound is normal as air circulates through the system. However, if you hear pulsating noises from the outdoor unit inside your home, there may be obstructions like twigs or damaged fan blades causing the issue.

Whirring Air Conditioner

HVAC fan making whirring sound

A whirring sound typically indicates a mechanical problem in the air conditioner’s indoor or outdoor unit. Possible causes include damaged belts, faulty fan blades, worn bearings, or a failing fan motor. Turn off the unit and call an HVAC technician for repairs.

Buzzing or Humming Air Conditioner

If a distinct humming or buzzing is coming from your outdoor unit, inspect for debris, such as leaves, flowers, or branches inside it. Clearing these obstructions is crucial. A buzzing sound might also indicate a deteriorating fan.

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Rattling Air Conditioner

Rattling noises often stem from parts loosening due to vibrations over time. Check and tighten screws and bolts on the unit. It’s also beneficial to clean the coils and replace the air filter. For optimal performance, consider scheduling annual maintenance with an HVAC professional.

Common HVAC Contractor Fixes for Loud Air Conditioning Units

Air conditioning service repairman

Continue reading to learn about common repairs for reducing air conditioner noise.

Cleaning and Straightening AC Unit Coil Fins

Maintaining clean coil fins is essential for optimal performance and efficiency. Schedule an annual tune-up with an HVAC contractor. During the visit, they can straighten bent coil fins using a fin comb and remove debris by utilizing a vacuum with a brush attachment to ensure your system runs smoothly.

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Securing Loose Air Conditioner Components

Given the numerous moving parts in an air conditioner, vibrations during operation are common. These vibrations can gradually loosen screws, eventually leading to noticeable rattling noises. Regular HVAC maintenance should include checking and tightening these screws to prevent disruptive sounds.

Clearing Debris from Condenser Fan Blades

HVAC outdoor unit depicting needing clearing fan blades debris

Access the interior of your air conditioner by opening the cabinet. Promptly remove any visible debris, particularly around the fan blades. Clearing foreign objects from this area is a straightforward task that helps maintain efficient operation.

Repairing Bent AC Unit Fan Blades

After cleaning out dirt and debris, inspect the fan blades for any irregularities. If blades are bent or uneven, they should be carefully straightened. It’s best to enlist an HVAC contractor for this task to ensure it’s done properly and to avoid exacerbating the issue. The contractor will meticulously adjust each blade to its correct alignment.

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Lubricating the Motor

Screeching sounds usually signify a need for motor lubrication, typically handled during regular tune-ups. An HVAC technician will apply suitable oil to essential parts, including the oil ports at the base of the fan motor, to alleviate noise and enhance function.

Steps Homeowners Can Take When Air Conditioners Make Loud Noises

wooden arrow nailed on a tree pointing right with next steps written on it depicting next steps to deal with air conditioner noise when starting

Continue reading to discover how homeowners can mitigate unusual noises from their air conditioning units.

1. Inspect the Outdoor AC Fan & Unit

Start by examining the condenser fan in the center of the outdoor unit. Check if it rotates freely and observe if the blades spin evenly without striking anything. Look for signs of debris inside the casing that might cause imbalance or contact. Also, inspect the coils and refrigerant piping. If you’re unsure about what you’re seeing, it’s safer to leave further inspections to a professional HVAC technician.

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2. Replacing Your HVAC Air Filters

Regularly changing air filters is crucial for maintaining your air conditioner’s efficiency. Clogged filters restrict airflow, forcing the unit to work harder, which may result in a humming noise. Homeowners should check their air filters monthly and replace them as necessary to ensure optimal functionality.

3. Maintaining Your Outdoor AC Unit

The outdoor unit of your air conditioning system is exposed to environmental elements. Before cleaning, turn off the unit for safety, open the case, and remove the top grille. Afterward, remove any debris from within. Ensure everything is secured when closing it back up.

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4. Evaluating the Run Capacitor

After cleaning, restart your air conditioner to check if the fan is operational. If the fan remains stationary, try to jumpstart it by nudging the blade with a long stick to generate momentum. If this action gets the fan spinning, it likely indicates a faulty run capacitor.

5. Checking Your Indoor Air Handler

indoor Air conditioner unit with ice buildup

If the outdoor unit seems fine, turn your attention to the indoor air handler. Look for any ice buildup or bent coil fins. For safety, turn off the power to allow any ice to thaw and the unit to dry before restarting it.

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6. Contact an HVAC Professional

While homeowners can manage many maintenance tasks to prevent air conditioner problems and reduce noise, some issues require professional expertise. If you’ve tried all the suggested fixes and the noise persists, it’s time to call in an HVAC expert.

Preventive Measures for Air Conditioner Starting Problems

Here are preventative steps you can take when you have AC starting problems:

Install Noise-Reducing Barrier

Noise from an air conditioner can disrupt your daily activities and interfere with your sleep. Consider installing a barrier such as a sound blanket or a noise-reducing fence to alleviate this. These solutions can significantly lower noise levels and improve your living environment. Consult with an HVAC contractor beforehand.

Schedule Regular HVAC Maintenance

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It’s essential to arrange for annual maintenance of your air conditioner. Experienced technicians can detect issues early on and provide timely interventions to prevent escalation. Their comprehensive cleaning eliminates the need for you to do it yourself, reducing the likelihood of loud noises developing in your AC unit.

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Call in an HVAC Expert

At the first indication of abnormal noise from your air conditioner, contact an HVAC contractor. Addressing these sounds promptly can prevent them from developing into more severe issues. Early interventions are typically more cost-effective than repairing extensive system failures.


Stay attuned to the sounds of your air conditioner; it often signals when something is amiss. Manufacturers design these systems to operate quietly, so any unusual noise should catch your attention. Familiarize yourself with the normal sounds of your AC to better identify anomalies. If you notice anything unusual, don’t hesitate to investigate. For complex issues, it’s prudent to consult a skilled HVAC technician.

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Contact Columbus Energies for Your HVAC Needs

Columbus Energies provides top-notch heating and cooling services across Southeastern Massachusetts and the Rhode Island region. Our highly qualified, professionally certified technicians can handle all your HVAC needs, from routine tune-ups and repairs to comprehensive installations and replacements. At Columbus Energies, we are committed to servicing your HVAC system with precision and care.

We pride ourselves on offering the most affordable HVAC services in the area. Our maintenance services aim to improve your comfort, boost your system’s energy efficiency, and help reduce your overall heating and cooling expenses. If you require an HVAC repair or are considering a new system, we will guide you in selecting the best option for your home that fits your budget. We stand behind our work with a robust satisfaction guarantee. Call Columbus Energies today to schedule your service appointment and receive free, in-home estimates.

At Columbus Energies, we stand behind our work with a solid satisfaction guarantee. For a free, in-home estimate or to schedule your service appointment, don’t hesitate to call Columbus Energies today.

Contact us now by calling (508) 674-1492 to speak to one of our home comfort specialists!

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