Why Is My Air Conditioner So Noisy? Common Causes and Solutions

Interestingly air conditioners produce different noises under different conditions. Additionally, noise levels also provide clues for evaluating an air conditioner’s performance and impact on it’s condition. 

Environmental Protection Authority, Victoria, has published noise guidelines for assessing noise levels from residential equipment. The document states the air conditioners must normally operate in the range of 20 db- 30 db. Above 55 db isn’t normal and the system must be evaluated and maintained. 

 Let’s explore different kinds of air conditioner noises. 

1. Rattling 

How does it feel like? 

• An intermittent sound that feels like small objects are shaking inside a container. 
• More prominent when turning the AC on or off. 
• Starts faintly and gets louder over time. 

Causes:

• Debris inside the AC unit. 
• Loose screws. 
• Failing motor fan. 

Solution: 

• Tighten or replace fasteners.  
• Replace the worn-out components.

2. Banging Sounds 

How does it feel like? 

• Heavy objects strike a surface inside the unit, usually in a rhythmic pattern. 
• The sound is more abrupt, loud, and repetitive. 

Causes:

• Misaligned or broken components. 
• Worn Out compressor.
• Disconnected motor mount. 
• Liquid slushing in the compressor. 
• Damaged or unbalanced blower wheel. 

Solution: 

• Inspect and identify the source of sound. 
• Tighten loose fan blades, straight the bent ones or replace broken ones. 
• Check, tighten or replace the damaged motor mounts. 
• Tighten the loosen ducts with duct tapes or brackets. 
• Contact a licensed technician to handle the compressor issues. 

3. Squealing 

How does it feel like? 

• Slightly softer than screeching, whistling or wheezing type sound, typically high pitched and more consistent than screeching. 
• Squealing sound continues as the system operates. 

Causes:

• Refrigerant leaks. 
• Worn or misaligned fan belt.
• Blower motor bearings. 
• Fan blade issues. 
• Faulty compressor. 
• Air flow restrictions. 

Solution: 

• Identify the source of sound. 
• Inspect and fix minor issues like tighten the loose fan belts, clean the filters and ductwork, lubricate bearings. 
• Call a professional for refrigerant leaks or compressor issues. 

4. Hissing 

How does it feel like? 

• Sound escaping from balloons or a faint “ssssssss” sound. 
• More persistent noise but can occasionally become more noticeable. 
• May occur continuously or can occur during certain periods. 

Causes:

• Refrigerant leak or high refrigerant pressure. 
• Internal valve issues. 
• Air leaks in ductwork. 
• Compressor issues. 

Solution: 

• Replace the malfunctioning valves. 
• Hire an AC specialist to check refrigerant leaks and check for weak points in refrigerant lines. 
• Inspect the ductwork for damages, seal the leaks using duct tape, metal patches or mastic sealant or replace the damaged sections. 
• Turn off the AC unit for safety hazards. 
• Hire a professional to fix the source of sound.

5. Buzzing 

How does it feel like? 

• Sound similar to the sound of a bee or fly. 
• A low-pitched sound that feels like a vibration or electric hum. 
• Can be intermittent or persistent. 

Causes:

• Loose or damaged components.
• Electrical arcing or irregular current flow. 
• Dirt and debris on condenser coils. 
• Refrigerant and compressor issues. 
• Blocked airflow due to clogged air filters. 

Solution: 

• Tighten loose components.
• Repair or change the damaged components. 
• Address the electric issues by repairing and replacing faulty internal components. 
• Clean the condenser coils with a cleaner and water hose. 
• Lubricate the motor bearings and repair or replace the fan motor. 
• Call the professional if the buzzing sound is loud and persistent or the sound is coming from the compressor. 

6. Whistling 

How does it feel like? 

• Resembles soft and sharp “whoosh or whistle”. 
• Typically high-pitched and sharp sound. 
• Can be intermittent or persistent. 

Causes:

• Clogged filters and ductwork. 
• Leaky and damaged ductwork. 
• Improperly sized ductwork. 
• Blocked or closed vents.
• Improper air conditioner installation. 
• Refrigerant leaks.
• High static pressure. 

Solution: 

• Inspect for airflow issues or pressure imbalances. 
• Inspect, clean, repair and replace air filters and ductwork.
• Resize ductwork.
• Ensure proper ventilation.
• Address refrigerant leaks.
• Balance static pressure. 
• Call a professional if the problem persists after basic troubleshooting and shows signs of reduced cooling efficiency or airflow.

7. Wheezing 

How does it feel like? 

• Mostly intermittent and softer than a whistling sound. 
• The sound resembles labored breathing or the air passing through an obstruction. 
• The AC system gives off uneven and irregular airflow, indicating strain on the system. 

Causes:

• Clogged or dirty filters.
• Blocked air vents or registers. 
• Improper ductwork size or design.
• Leaky ductwork.
• Dirty or clogged evaporator coil. 
• Refrigerant issues. 
• Malfunctioning blower motor or fan.

Solution: 

• Maintain the airflow by cleaning filters, vents, and registers and removing obstructions. 
• Assess ductwork size and design. 
• Repair and replace the blower motor.
• Clean evaporator coil. 
• Address refrigerant issues. 

8. Screeching 

How does it feel like? 

• Resembles the sound of metal or rubber grinding together. 
• Usually high-pitched or harsh. 
• Sound is intermittent or persistent when the AC is running. 

Causes:

• Dry or faulty bearings in the fan or blower motor. 
• Worn out or damaged fan belt. 
• Debris in fan blade. 
• Overheating motor. 
• Improper component alignment. 
• Low refrigerant levels. 
• Loose or damaged parts. 

Solution: 

• Replace or adjust the fan belt. 
• Lubricate and replace fan and blower motor bearings. 
• Realign the internal components, especially the fan. 
• Address overheating motors. 
• Check the refrigerant levels and refill if low. 
• Lubricate the bearings or replace the damaged ones. 
• Tighten the fan belt, and inspect and fix minor issues. 
• Contact licensed technicians to fix compressor issues. 

9. Gurgling 

How does it feel like? 

• Bubbling or splashing sound of liquid passing through the pipes. 
• Intermittent or continuous. 
• Can be soft and low-pitched or become louder depending on the severity of the problem. 

Causes:

• Air in the refrigerant lines.
• Low refrigerant levels.
• Dirty or clogged condensate drain.
• Dirty or blocked evaporate coil.
• Improper installation or faulty system design. 
• Issues with expansion valves. 

Solution: 

• Check and refill refrigerant if low.
• Ensure proper refrigerant charging. 
• Inspect and repair air leaks in refrigerant lines.
• Clean the condensate drain. 
• Clean the evaporator coil. 
• Repair or replace the expansion valve. 

10. Clicking 

How does it feel like? 

• Rhythmic noise resembling the sound of a switch being turned on and off. 
• Sound can be occasional or repetitive, relatively soft or pronounced depending on the cause and severity of the situation. 

Causes:

• Frequent turning on and off of the thermostat.
• Electrical relay switching.
• Loose or debris in the fan blades. 
• Problems in blower motor. 
• Contraction or expansion in AC components due to excessive cooling. 
• Fault capacitor.
• Problems with electric circuit board or contactor of the AC. 

Solution: 

• Check the thermostat and relay. 
• Inspect and clean the fan blades.
• Examine the motor blower.
• Tighten or replace loose components.
• Replace the capacitor.
• Inspect for expansion or contraction air conditioner noises. 
• Repair or replace the electric circuit board. 
• Contact a professional AC technician if the AC doesn’t turn on or is short cycling. 

11. Popping 

How does it feel like? 

• Sharp snapping sound, resembling a gunshot or a cork being pulled. 
• Single loud noise or intermittent, depending on the cause. 
• Can be normal due to sudden changes in pressure, temperature, or movement of materials within the 

Causes:

• Contraction and expansion of ductwork. Often due to improperly sized or installed ducts. 
• Airflow obstructions in ductwork.
• Contraction and expansion of evaporator coil or condenser or release built-up pressure.
• Dirt, ice build up, or issues with refrigerant flow in the evaporator coil or condenser coil.
• Electrical issues such as electrical arcing or sparking in the system, often due to faulty wiring, a damaged capacitor, or a malfunctioning circuit board.
• Improper installation and loose components of the air conditioner units or ductwork.

Solution: 

• Insulate the ductwork to stand temperature and pressure changes, use flexible material.
• Clear airflow obstructions.
• Replace the dirty and clogged filters.
• Inspect and fix refrigerant issues.
• Clean or repair coils.
• Fix electrical issues. Take professional help for electric work.
• Tighten loose components. 

12. Clunking 

How does it feel like? 

• Typically a deep, heavy noise caused by two heavy objects hitting together, or heavy dropping inside the unit. 
• Often irregular. Mostly occurs when a unit starts, stops or operates. 

Causes:

• Debris inside the unit. 
• Loose or broken fan blades.
• Faulty or worn-out motor mounts.
• Imbalance or loose blower wheel. 
• Loose or broken compressor components.
• Worn-out bearings or belts.
• Improper installations.

Solution: 

• Remove debris from the AC unit.
• Check and secure fan blades. 
• Balance or replace the blower wheel.
• Inspect and repair motor mounts.
• Replace worn-out bearings and belts.
• Address the compressor issues. 
• Tighten and reinstall loose parts.