A knocking sound from an AC blower motor signals possible problems. Main causes include an imbalanced motor, a failing motor, worn-out bearings, and installation issues. Additionally, undersized ductwork and compressor failure can lead to unusual sounds in the HVAC system.
Addressing the issue starts with inspection. First, turn off the AC unit. Then, check for loose screws or brackets. Tighten or replace them if necessary. Next, clear any debris obstructing the blower motor. Lastly, assess the bearings for wear. If they are worn-out, consider replacing the blower motor altogether.
Understanding the causes and solutions for an AC blower motor knocking sound can help ensure smooth operation. Regular maintenance and timely repairs can extend the life of your unit. If the problem persists, consulting a professional technician is advisable for further diagnosis.
Next, we will explore specific troubleshooting steps and tools that can assist in effectively managing these sounds and issues.
What Is an AC Blower Motor Knocking Sound and Why Does It Matter?
An AC blower motor knocking sound is an unusual noise that occurs during the operation of an air conditioning system. This sound typically indicates a malfunction or issue with the blower motor or its components.
The American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) states that a well-functioning blower motor should operate quietly, without any disruptive noises. Noises such as knocking can signal mechanical problems that require attention.
Knocking sounds may arise from loose or damaged components, such as the blower wheel or motor mounts. They may also indicate obstructions within the blower assembly. Identifying the source of the noise is crucial for maintaining system efficiency.
The International Institute of Refrigeration describes that mechanical wear, accumulation of dirt, or imbalance in the blower wheel can lead to knocking sounds. Regular maintenance can help mitigate these issues.
Data from the U.S. Department of Energy indicates that about 20-30% of energy efficiency loss in HVAC systems occurs due to mechanical issues, including blower motor problems. Proactive maintenance can improve energy efficiency and extend the lifespan of the system.
AC blower motor knocking can lead to increased energy bills, reduced comfort, and eventual system failure. Ignoring these sounds may also result in more significant repairs and replacements.
The broader implications include increased energy consumption, potential health impacts from inadequate air circulation, and economic burdens on households due to higher repair costs.
Examples of these impacts include higher utility bills and decreased indoor air quality, leading to respiratory issues.
Reputable organizations like the Air Conditioning Contractors of America recommend regular equipment inspections and timely repairs. Homeowners should schedule annual maintenance checks to identify potential issues early.
Strategies to minimize knocking sounds include ensuring that all components are securely fastened, cleaning the blower assembly, and replacing worn parts as necessary. Regular check-ups and prompt actions can mitigate these problems.
What Are the Common Causes of an AC Blower Motor Knocking Sound?
The common causes of an AC blower motor knocking sound can include several mechanical and operational issues.
- Loose blower assembly
- Debris in the blower fan
- Worn motor bearings
- Faulty motor mounting brackets
- Imbalanced blower wheel
- Electrical issues
Examining these causes can help identify the problem. Each issue can lead to different symptoms or severity, which impacts the performance of the AC system.
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Loose Blower Assembly: A loose blower assembly can create rattling or knocking sounds when the motor operates. This condition occurs when mounting screws or bolts become loose over time. The noise can vary in intensity and may worsen as the system works harder.
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Debris in the Blower Fan: Debris such as leaves, dust, or other foreign objects can get lodged in the blower fan. This obstruction can disrupt the fan’s rotation, leading to knocking or clanking noises. Regular maintenance can help prevent this issue by ensuring the fan is clean and unobstructed.
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Worn Motor Bearings: Worn bearings can cause metal-to-metal contact within the motor. This phenomenon leads to a knocking or grinding sound during operation. Over time, this wear can result in more significant issues, including motor failure.
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Faulty Motor Mounting Brackets: Motor mounting brackets that are damaged or misaligned can lead to improper motor support. This issue can cause the motor to vibrate excessively, resulting in knocking sounds. Inspecting and securing these brackets can mitigate the problem.
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Imbalanced Blower Wheel: An imbalanced blower wheel can cause vibrations that produce a knocking noise. This imbalance can occur due to damaged or missing blades. A technician can usually correct this by adjusting or replacing the blower wheel.
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Electrical Issues: Electrical problems, such as issues with power supply or control circuits, can also lead to irregular operating sounds. This condition might manifest as a knocking sound if the motor struggles to achieve the correct speed.
By identifying the specific cause of the knocking sound, homeowners can take appropriate measures to repair the system, improving efficiency and prolonging the AC’s lifespan.
How Can Loose or Worn Blower Motor Mounts Cause Knocking?
Loose or worn blower motor mounts can lead to knocking sounds due to improper alignment and excessive vibrations during operation. This situation affects the overall performance of the blower motor and can potentially cause further damage.
When blower motor mounts become loose or worn, several key issues arise:
- Misalignment: Loose mounts can cause the blower motor to be misaligned. This misalignment leads to uneven operation, which creates knocking sounds as the motor vibrates against other components.
- Increased vibrations: Worn mounts do not absorb vibrations effectively. As a result, the motor generates more vibrations, which translate into noise that can be perceived as knocking.
- Contact with other parts: A misaligned or vibrating blower motor can come into contact with surrounding components. This contact generates additional noise and may cause cosmetic or structural damage to those parts.
- Reduced efficiency: Excessive vibration may reduce the efficiency of the blower motor. The motor might struggle to perform its intended function, leading to inadequate airflow and further mechanical stress.
- Potential for greater damage: Continual knocking from a loose or worn blower motor can lead to more severe mechanical failures. Over time, this can necessitate expensive repairs or a complete motor replacement.
Addressing these issues typically involves inspecting the mounts, tightening them if loose, or replacing them if they are excessively worn. Regular maintenance can help prevent the development of knocking sounds caused by blower motor mount issues.
Why Do Debris and Obstructions Lead to Knocking Sounds in AC Units?
Debris and obstructions can lead to knocking sounds in air conditioning (AC) units because they interfere with the internal components of the system. When foreign objects are present, they can cause components to hit against each other, resulting in distinct knocking or banging noises.
The U.S. Department of Energy defines air conditioning as a system that controls the temperature and humidity of indoor air through the use of refrigeration and ventilation. A functioning AC system relies on the smooth operation of its components, such as the blower motor and fan.
Several factors contribute to knocking sounds in AC units. First, debris can accumulate inside the unit, such as leaves, dirt, or small objects. This accumulation can obstruct the moving parts, preventing them from functioning correctly. Additionally, loose components, such as screws or bolts, may also lead to rattling or knocking as parts vibrate during operation. Lastly, worn-out or damaged bearings in motors can create a knocking sound as they struggle to maintain proper rotation.
Technical terms like “bearings” refer to components that help reduce friction between moving parts. When bearings wear down, they can allow parts to move excessively, causing noise. “Obstruction” implies something that blocks a pathway or function, leading to malfunctions in the system.
Mechanically, when foreign objects obstruct the fan or other moving parts, they restrict airflow or physical movement. Motors work by rotating, and when obstructed, they may hit against stationary objects. Over time, constant knocking can lead to further damage, potentially resulting in expensive repairs.
Specific conditions that contribute to knocking sounds include inadequate maintenance, which allows debris to build up. For example, if an AC unit is installed near a tree, falling leaves can accumulate inside the unit if not regularly cleaned. Additionally, poor installation can lead to loose components that vibrate and create noise during operation. Regular checks and preventive maintenance can help mitigate these issues.
What Happens When a Blower Motor or Bearings Fail?
When a blower motor or bearings fail, the heating or cooling system can become inefficient or inoperable. The consequences can include reduced air quality, higher energy costs, and damage to other components.
The main points related to blower motor or bearing failure include:
1. Symptoms of failure
2. Causes of failure
3. Consequences of failure
4. Repair options
5. Preventive measures
Understanding these aspects will help in diagnosing and addressing blower motor or bearing issues.
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Symptoms of Failure:
Symptoms of blower motor or bearing failure include unusual noises, reduced airflow, and inadequate heating or cooling. A knocking or grinding sound may indicate bearing wear, while silence may suggest a motor failure. According to HVAC experts, noticeable vibrations can also imply bearing wear, and warm spots in rooms may signal airflow issues from a malfunctioning blower. -
Causes of Failure:
Causes of blower motor or bearing failure often involve issues such as electrical overload, dust accumulation, or overheating. Electrical problems can arise from faulty connections or short circuits. Dust build-up can hinder performance and lead to overheating. The U.S. Department of Energy emphasizes the importance of regular maintenance to mitigate wear and tear on these components. -
Consequences of Failure:
Consequences of blower motor or bearing failure can include decreased energy efficiency, higher utility bills, and potential damage to the HVAC system. A malfunctioning blower can cause the system to work harder, leading to increased energy consumption. Additionally, neglecting repairs can exacerbate problems, resulting in costly system replacements. -
Repair Options:
Repair options for a failing blower motor or bearings include lubrication, replacement of bearings, or full motor replacement. If bearings exhibit wear, replacing them may be a cost-effective solution. However, when the motor itself fails, replacement is typically necessary. A study by the U.S. Environmental Protection Agency highlights that timely repairs can yield significant energy savings. -
Preventive Measures:
Preventive measures can help prolong the life of blower motors and bearings. Regular maintenance, including cleaning and inspection, is crucial. Replacing air filters and ensuring proper airflow can reduce strain on these components. HVAC professionals advise scheduling seasonal check-ups to catch issues early and maintain optimal performance.
By recognizing these factors, homeowners can better respond to blower motor or bearing failures, ensuring efficient system operation and longevity.
What Types of Noises Are Associated with AC Blower Motors?
AC blower motors can produce various noises, which indicate different underlying issues. Common noises include grinding, squeaking, rattling, and buzzing sounds.
- Grinding noise
- Squeaking noise
- Rattling noise
- Buzzing noise
- Whistling noise
- Humming noise
Understanding these noises allows homeowners to diagnose problems early and choose appropriate solutions to avoid costly repairs.
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Grinding Noise:
Grinding noise occurs when metal parts come into contact due to worn-out bearings or other mechanical failures. This noise indicates that the blower motor is straining to operate. According to HVAC experts, ignoring grinding sounds can lead to complete motor failure and costly replacements (Davis, 2020). Regular inspections can identify issues that may cause grinding. -
Squeaking Noise:
Squeaking noise often comes from dry or damaged bearings that require lubrication. It can also indicate a slipping belt in the system. Immediate action can prevent further damage. A study by the Department of Energy suggests that lubricating bearings can increase motor life by 30% (Smith, 2021). Servicing the blower motor regularly can ensure smooth operation. -
Rattling Noise:
Rattling noise can result from loose screws or loose housing around the blower motor. It may also be caused by debris caught in the fan. This noise should not be ignored, as it can lead to additional damage. Professional HVAC technicians recommend regular maintenance checks to secure components and prevent rattling sounds (Johnson, 2019). -
Buzzing Noise:
Buzzing noise can indicate electrical issues, such as a faulty capacitor or wiring problems. It may also signal that the motor is drawing excessive current. Ignoring buzzing can lead to electrical fires or motor burnout. The National Fire Protection Association emphasizes the importance of addressing electrical noises promptly (Jones, 2020). -
Whistling Noise:
Whistling noise may emerge when air escapes through gaps or leaks in the ductwork. This affects efficiency and causes strain on the motor. Small leaks can lead to significant energy waste. A study by the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) indicates that sealing ductwork can improve system efficiency by up to 20% (Taylor, 2018). -
Humming Noise:
Humming noise from an AC blower motor may indicate that it is working but could also hint at an issue with the transformer or the motor’s windings. Regular maintenance is critical to identify potential electrical faults before they escalate into larger problems. The importance of proactive electrical system checks is stressed in the HVAC Inspection Guide (Smith, 2021).
How Can You Diagnose the Source of a Knocking Sound in Your AC Blower Motor?
To diagnose the source of a knocking sound in your AC blower motor, inspect the motor assembly, check for loose parts, examine the blower wheel, and assess the installation.
Inspecting the motor assembly is crucial. A knocking sound often indicates that the motor is out of alignment or has worn bearings. Check for any visible damage or unusual wear on the mounting brackets. Loose connections can also lead to vibrations that produce knocking sounds.
Checking for loose parts is essential. Ensure that all screws, nuts, and bolts are tightly secured. Over time, vibrations can loosen these fasteners, causing parts of the motor to move and generate noise.
Examining the blower wheel should be a priority. Debris stuck in the blower wheel can create imbalance, leading to knocking noises. Remove any obstructions and ensure the wheel spins freely without touching other components.
Assessing the installation will help ensure that the blower motor is properly mounted. Improper installation can lead to misalignment, causing unnecessary noise. Verify that the motor aligns correctly with the ductwork and surrounding components.
Taking these steps will help identify the source of the knocking sound and allow for appropriate repairs or adjustments to restore normal operation of the AC blower motor.
What Tools Are Essential for Inspecting an AC Blower Motor?
The essential tools for inspecting an AC blower motor include a multimeter, screwdrivers, wrenches, and a vacuum cleaner.
- Multimeter
- Screwdrivers
- Wrenches
- Vacuum cleaner
- Safety goggles
- Contact cleaner
- Torque wrench
These tools help ensure a thorough and effective inspection of the AC blower motor, which can lead to better performance and longevity of the system.
Multimeter: A multimeter is a device used to measure electrical voltage, current, and resistance. It helps technicians check if the blower motor is receiving adequate power and operating correctly. By measuring the voltage at the motor terminals, a multimeter can confirm whether the electrical supply is sufficient. For example, a typical blower motor requires a specific voltage range, often around 120V for residential units.
Screwdrivers: Screwdrivers are essential for accessing the blower motor. Technicians use them to remove screws from covers or panels. Having both flathead and Phillips screwdrivers ensures that the technician can handle various screw types. Notably, organizing different sizes can speed up the inspection process and reduce frustration.
Wrenches: Wrenches are crucial for loosening or tightening bolts that secure the blower motor in place. Adjustable wrenches can accommodate various nut sizes, providing versatility. Properly securing bolts is vital because loose screws can lead to vibrations and increased wear on motor components.
Vacuum cleaner: A vacuum cleaner is necessary for cleaning debris from around the blower motor and its components. Dust and dirt can restrict airflow and cause overheating. Keeping the motor clean ensures efficient operation. Regular maintenance with a vacuum can extend the lifespan of the blower motor.
Safety goggles: Safety goggles protect technicians’ eyes from dust, debris, and accidental splashes during the inspection. By wearing safety goggles, technicians can ensure their safety while troubleshooting and repairing systems.
Contact cleaner: Contact cleaner is an aerosol product used to clean electrical contacts. It helps remove corrosion and dirt buildup that can affect motor reliability. A clean connection is vital for optimal electrical performance, and periodic use of contact cleaner can prevent future issues.
Torque wrench: A torque wrench ensures that bolts are tightened to the manufacturer’s specifications. Proper torque is important because overtightening can damage components, while undertightening may lead to loose connections. Using a torque wrench can significantly enhance the reliability of the blower motor installation.
These tools collectively play an essential role in inspecting and maintaining an AC blower motor, leading to better efficiency and performance. By understanding how each tool functions, technicians can effectively diagnose and resolve issues related to blower motors.
How Can You Determine the Specific Cause of Knocking Noises?
Knocking noises in a vehicle can arise from various sources, and determining the specific cause requires careful observation and diagnostic steps. Follow these detailed explanations to identify the potential causes of knocking noises:
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Engine Issues: Knocking sounds can indicate engine problems. This may result from inadequate lubrication or worn engine components. Insufficient oil levels can cause metal parts to rub against each other, creating knocking sounds. According to the American Automobile Association (AAA, 2021), low oil levels should be addressed immediately to prevent severe engine damage.
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Detonation: Also known as “knock,” this occurs when fuel combusts prematurely in the engine’s cylinders. High octane fuels can help prevent this. A study by the Society of Automotive Engineers (SAE, 2020) notes that excessive engine temperatures can promote detonation, which manifests as knocking noises.
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Suspension Problems: Worn or damaged suspension components can also emit knocking sounds. Parts like shock absorbers, struts, or bushings can degrade over time. Research published in the Journal of Mechanical Engineering (Smith et al., 2019) emphasizes that regular inspection of suspension systems is crucial for vehicle safety and noise reduction.
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Loose Components: Loose engine mounts or exhaust systems can shake during vehicle operation. This vibration can produce knocking noises as parts come into contact. Maintenance checks can identify and tighten these components, reducing noise levels significantly.
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Transmission Trouble: A malfunctioning transmission can generate knocking sounds, especially during shifting. Problems may include worn gears or low transmission fluid. According to a 2022 report by Automotive News, regular transmission fluid checks are essential to ensure smooth operation and avoid adverse sounds.
By assessing these areas systematically and obtaining necessary inspections, vehicle owners can pinpoint the specific cause of knocking noises and address them promptly.
What Steps Should You Take to Fix a Knocking Sound in Your AC Blower Motor?
To fix a knocking sound in your AC blower motor, follow these critical steps: inspect for loose components, check for foreign objects, examine the fan blades, and consider professional intervention if necessary.
- Inspect for loose components
- Check for foreign objects
- Examine the fan blades
- Consider professional intervention
Understanding these steps is essential for effectively resolving the issue. Each step addresses a specific aspect of the problem and can help identify the source of the knocking sound.
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Inspect for Loose Components:
Inspecting for loose components is a vital first step in diagnosing a knocking sound in your AC blower motor. Loose screws, bolts, or brackets can create vibrations that produce noise during operation. According to HVAC experts, addressing minor loose components can often resolve the issue without further complications. For instance, a study conducted by the American Society of Heating, Refrigerating and Air-Conditioning Engineers reported that nearly 25% of noise complaints are due to untightened parts. -
Check for Foreign Objects:
Checking for foreign objects is also important in diagnosing the knocking sound. Dirt, debris, or other unwelcome items caught within the blower can interfere with its function and create noise. Regular maintenance and cleaning can prevent this issue. A case study by the Indoor Air Quality Association highlighted that over 30% of blower motor problems stem from blocked components. It is advisable to perform checks at least twice a year to avoid repetitive issues. -
Examine the Fan Blades:
Examining the fan blades ensures they are straight, undamaged, and securely attached. Bended or broken blades can catch on the housing, leading to knocking sounds. Properly functioning fan blades promote effective airflow and noise reduction. The National HVAC Association suggests that fan blade issues account for approximately 15% of blower motor noise complaints. Regular inspections can help identify damage early. -
Consider Professional Intervention:
Considering professional intervention may be necessary if the previous steps do not resolve the noise. Problems such as worn bearings, motor failure, or other complex mechanical issues often require professional expertise. According to the U.S. Department of Energy, attempting to repair intricate motor components without proper knowledge can lead to further damage, thus increasing repair costs. Professional services also provide peace of mind that repairs are performed correctly.
How Can You Properly Tighten or Replace Blower Motor Mounts?
To properly tighten or replace blower motor mounts, you should follow a systematic approach that includes safety precautions, identification of the correct tools, and precise installation techniques.
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Safety precautions: Always disconnect power to the blower motor. This prevents any accidental starting or electrical hazards while working. Ensure you wear safety gloves and goggles to protect yourself from debris.
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Tools required: Gather the necessary tools before beginning. Commonly used tools include wrenches, sockets, ratchets, a torque wrench, and a screwdriver. Using the right tools simplifies the process and ensures proper installation.
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Inspect the existing mounts: Check for signs of wear, damage, or deterioration on the blower motor mounts. Cracks or excessive movement can indicate that replacement is necessary. A study in the Journal of Mechanical Engineering (Smith, 2021) notes that worn mounts can lead to increased vibrations and noise, affecting the motor’s efficiency.
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Removal of the old mounts: Loosen the screws or bolts securing the mounts, using the appropriate wrench or socket. Remove the mounts carefully to prevent damage to surrounding components.
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Installing new mounts: Position the new mounts in their place. Use a torque wrench to tighten the bolts to the manufacturer’s specifications. This ensures that the mounts are securely fastened without risking damage from overtightening. Specifications can often be found in the service manual specific to the vehicle or equipment.
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Final inspection and testing: Once everything is installed, perform a visual inspection to ensure all components are secure. Reconnect the power and test the blower motor to confirm it operates smoothly without excessive vibrations or noise.
Following these steps will ensure proper installation and functionality of your blower motor mounts.
What Maintenance Tips Can Help Prevent Knocking Sounds in AC Systems?
The maintenance tips that can help prevent knocking sounds in AC systems include routine inspections, tightening loose components, checking for debris, maintaining proper lubrication, and ensuring level installation.
- Routine inspections
- Tightening loose components
- Checking for debris
- Maintaining proper lubrication
- Ensuring level installation
These maintenance practices are essential as they directly contribute to the efficient operation of an AC system, minimizing the risk of knocking sounds associated with mechanical issues.
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Routine Inspections: Conducting routine inspections helps identify potential problems before they escalate. Technicians can check for wear and tear on parts, ensuring everything functions as intended. Regular checks allow for early detection of issues such as loose components or misalignments. According to the U.S. Department of Energy, regular maintenance can improve an AC system’s efficiency by up to 15%, significantly reducing operational noise.
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Tightening Loose Components: Loose parts can vibrate and create knocking sounds. Ensuring all screws, bolts, and connections are secure prevents unnecessary movement during operation. For example, a study by HVAC industry experts in 2022 highlighted that tightening loose components reduced noise levels in most AC units by 20%. Maintaining component integrity assures that mechanical parts operate smoothly without friction.
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Checking for Debris: Debris accumulation can obstruct airflow or interfere with moving parts. Regularly clean air filters and remove debris from around the unit to ensure proper airflow. The American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) recommends a monthly check of filters and surroundings to minimize obstruction-related noises. Failure to do so can exacerbate knocking sounds due to increased stress on the AC system.
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Maintaining Proper Lubrication: Lubrication of moving parts reduces friction and minimizes noise. Regularly lubricating components such as fans and motors ensures smooth operation and reduces wear on moving parts. The National Association of Broadcasters (NAB) states that appropriate lubrication can decrease noise levels by approximately 15-30%, enhancing overall system performance.
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Ensuring Level Installation: An uneven installation can lead to vibration and knocking sounds. It is crucial to ensure that the AC unit is level for optimal operation. Proper leveling reduces stress on components and minimizes noise generation. According to research from the Mechanical Systems Engineering Journal, units installed on uneven surfaces experienced 25% more noise complaints compared to level installations. Regular checks should confirm proper positioning and stability.
Incorporating these maintenance tips into a routine schedule can effectively prevent knocking sounds in AC systems and prolong their lifespan.
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