What Should You Do if Your Cooling System Is Making Weird Noises?

Loud noises from the home’s central air conditioner can be quite alarming, especially when the air conditioner noises you hear occur out of nowhere. A new and sudden noise may be a sign there is something wrong with your indoor air conditioning unit or the outdoor unit, and service may be needed to fix repair issues, or a component needs to be replaced.

This summer, listen for noises coming from your air conditioner beyond the normal steady humming you are used to, such as a high-pitched squealing noise, banging noise, clicking noise, buzzing noises, and rattling sounds. Any unusual noises you hear could mean repair problems such as a refrigerant leak, high internal pressure inside the compressor, a loose fan belt or other loose parts, worn bearings within the indoor or outdoor fan motor, and other service issues.

Williams Comfort Air shares what specific air conditioning noises could mean and what you should do when you notice these sounds. Call a professional right away for repair services to protect your system when your air conditioner is making funny noises.

Banging Noise from Your Air Conditioner

If you hear banging noise or rattling from within your indoor or outdoor air conditioning unit, it’s usually created by loose parts. Typically, an air conditioner making banging sounds is due to loose parts originating within the indoor blower fan or outdoor compressor. When you hear the banging sounds from your indoor equipment, there may be loose fan blades causing the blower fan to generate excess noise as it runs. If the noise seems to come from inside the compressor, it’s likely a loose or broken connector rod or piston pin.

What to Do

Loose parts require repair right away. Continuing to operate your air conditioner with broken or loose components can cause further damage to your central air system, requiring more extensive and costly repair services. Call a professional to diagnose and fix the cause of banging sounds coming from your air conditioner equipment. Loose fan blades within the blower or condenser fan may be reset during repair. If there are loose components inside the compressor unit, the compressor itself will usually require replacement.

Clanking Sounds from AC Units

Just like banging, clanking noises from your air conditioner can also be caused by loose parts or broken components within the indoor or outdoor equipment. Alternatively, a loud clanking sound from the indoor blower fan or outdoor condenser fan can tell you the fan blades are out of balance. If the blades are unbalanced, they will strike neighboring components as the fan spins.

What to Do

If you have an air conditioner making clanking noises, shut down your air conditioner and call for repair services. If you continue to run your air conditioning system while your air conditioner is making clanking sounds, the off-balance blades within the blower fan or condenser fan could inflict more damage upon your cooling unit.

Clicking Noise from Your Air Conditioner

A quick-clicking noise is normal as your air conditioning system starts and ends a cooling cycle. However, if the clicking noise continues as the air conditioner runs, these noises indicate potential system problems. Clicking could be caused by a failing thermostat or electrical problem. An air conditioning unit has various electrical connections and components which control different aspects of system operation, such as the fan motor relay switch or compressor capacitors.

What to Do 

If you suspect an electrical problem or bad thermostat, call for professional services. Our NATE-certified air conditioner repair technicians are able to diagnose the source of a clicking noise within your system and fix the necessary components. We test thermostat function to determine if this control has gone bad and will install a new thermostat unit right away so you can maintain efficient control over your home’s air conditioner.

Buzzing Noise from Outdoor Unit

A buzzing noise is often heard from the outdoor unit of a home’s air conditioner system. Buzzing noises may mean a few common air conditioner issues.

  • Compressor malfunction – the compressor isn’t working correctly, which could be due to an electrical problem or improper amperage of electrical voltage from the relay switch. 

  • Loose or damaged isolation feet – the compressor sits atop rubber isolation feet within the outdoor unit. If these feet are damaged or become loose, a buzzing noise can occur during a cooling cycle. 

  • Condenser fan malfunction – the condenser fan runs via a fan motor in the outdoor air conditioning unit. If the fan motor isn’t working properly, you may hear buzzing. Fan motor operation may be disrupted by debris in the unit, electrical issues, or simply the motor is going bad.

If you hear buzzing from indoor components, you may have a:

  • Frozen air conditioner – Your air conditioner evaporator coils may freeze, producing buzzing noises. Poor air movement due to debris or a dirty air filter, leaks in the refrigerant piping, a faulty expansion valve, and other system issues can cause the coils to form ice or frost, resulting in buzzing from the unit.

What to Do

Compressor malfunctions, electrical issues, and damaged isolation feet require professional repair services to fix, as components or the entire compressor may need to be replaced.

If the buzzing is the result of a frozen air conditioner, take these steps to thaw the system.

  1. Adjust thermostat heating cooling settings from COOL to OFF. Keep the air conditioning system off and allow ice on the coils to thaw.
  2. At the thermostat switch the fan setting from AUTO to ON. Run the fan constantly to move warm air over the coils, which will help melt ice buildup.
  3. Check and change your air filter, if necessary. A dirty filter is a common reason air conditioners freeze, as the filter blocks proper air flow through the system.
  4. Once the coils are completely thawed, turn the air conditioner back on and allow it to run. If it continues to freeze, turn off the system and call for repair service. 

Squealing Noise from Air Conditioners

High-pitched squealing sounds from air conditioners are usually the result of bad bearings in the blower fan or outdoor fan motor or a slipped fan belt within the blower.

  • Bearings in a fan motor require regular lubrication, which is typically a part of seasonal air conditioner maintenance. The condenser fan and blower fan operate using a fan motor. If the bearings are dry, squealing or a grinding noise result as metal moves across metal – squealing is a common sign of poor maintenance.

  • In older air conditioning units, the blower fan motor is attached to the blades by a fan belt. If the fan belt slips out of position on the pulleys, the air conditioner produces squealing noises as it runs. 

Rarely, squealing from the outdoor unit indicates high internal pressure inside the compressor. Squealing will occur at the beginning of an air conditioning cycle and last around 10 to 15 seconds before stopping. High-pitched squealing due to high internal pressure is caused by a heating-cooling refrigerant leak or other malfunctions.

What to Do

If you experience squealing air conditioning noises at the beginning of the system’s cooling cycles, turn off the air conditioning system right away. Call your trusted heating-cooling contractor to schedule repair services as soon as possible. High pressure within the compressor can be dangerous and needs to be corrected immediately.

If you experience squealing air conditioning noises from a fan belt or fan motor, call a professional to schedule an annual maintenance tune-up if you haven’t already done so this season. Your technician will lubricate motor bearings as needed. Or you can do so yourself.

Condenser fan motor:

  1. Turn off electrical power to the outdoor unit.
  2. Unscrew and remove the cover at the top of the condenser unit.
  3. The condenser fan is mounted to the cover or to a cage assembly within the outdoor unit. Turn the component over to locate the motor oil ports at the top and/or bottom of the component and remove the port plugs.
  4. Fill each port with oil until oil backs up from the opening. Wipe up spilt oil.
  5. Replace port plugs, reposition the cage assembly if applicable, and replace the cover.
  6. Restore electrical power to the unit.

Blower fan motor:

  1. Turn off electrical power to the indoor unit.
  2. Remove the metal panel to access the blower cabinet.
  3. If there is an electrical circuit board in front of the blower assembly, unscrew it and move it out of the way. Remove the mounting bolts holding the blower assembly in place and remove it from the cabinet.
  4. Locate the oil ports on the fan motor. Remove port plugs and insert two to three drops of oil Replace caps.
  5. Replace the blower assembly within the cabinet, tighten bolts, and replace circuit board if applicable. Replace access panel.
  6. Restore electrical power to the unit.

To fix a slipped fan belt:

  1. Turn off electrical power to the indoor unit.
  2. Remove the access panel to the blower cabinet.
  3. Reposition the slipped fan belt back onto the motor pulleys.
  4. Test the fan belt tension by pressing down in the middle of the fan belt. If it deflects ¾-inch or more, it needs to be tightened.
  5. Adjust the nuts on the motor’s side or base. Turn them counterclockwise to loosen the motor so you can move it.
  6. Slide the motor backwards to tighten the belt.
  7. Once the fan belt is taut, retighten the nuts. Recheck tension – the belt should deflect only ½ to ¾ inches.
  8. Replace the access panel.
  9. Restore power to the indoor air conditioner unit.

Hissing Sounds Coming from Air Conditioners

A constant hissing noise from your air conditioner often indicates a refrigerant leak. Within the system, the refrigerant is under pressure, which causes it to crease a hissing sound or bubbling noise as it escapes the system. A refrigerant leak can occur due to damage to the copper lines connecting your indoor and outdoor equipment, or a faulty expansion valve within the system.

In some cases, hissing signals pressure buildup within the compressor. Before the loud noises turn to squealing, hissing can be heard as pressure builds.

What to Do

If you suspect a refrigerant leak, call for repair service right away. When a leak allows refrigerant to escape the system, your air conditioner does not have enough coolant to properly cool your home’s air. Holes in refrigerant piping allow refrigerant to spill out into the environment – if your air conditioner is older and still uses Freon (R-22) refrigerant, this is dangerous to the environment. Your technician is able to pinpoint the source of the leak, fix it, and recharge the system with the proper amount of refrigerant.

If You Notice Air Conditioner Noises…

If you experience any of the air conditioner noises outlined above, stop the sound when you call Williams Comfort Air for repair services. We perform repairs on all air conditioner makes and models throughout the Indianapolis area. Contact us today to schedule service.

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