If Your Air Conditioner Is Making Weird Noises, Here’s What to Do

A/C Weird Noises

If you hear loud noises that your air conditioner is making, you probably wonder if these sounds are normal. When air conditioning noises differ from the usual humming you’re used to hearing from your indoor air handler or outdoor unit, the sounds you hear could mean common air conditioning issues that require repair services to fix.

High pitched squealing noise, banging noise, clicking noise, buzzing noise, hissing noise, rattling noise, and other loud sounds coming from your air conditioner all mean there is something within the system that needs to be replaced or repaired. A fan motor, blower fan, condenser fan, fan belt, expansion valve, relay switch, compressor, refrigerant piping, and other parts can make such noises when they malfunction.

Listen for troublesome loud noises like squealing, buzzing, rattling, hissing, and banging from indoor and outdoor central air conditioner equipment this summer. Thomas & Galbraith explains causes of the most common air conditioner noises and what needs to be done to fix issues. When you need to call a professional for air conditioning repair services, turn to our team to investigate system sounds and put an end to your worries over an air conditioner making unusual operating noise.

Banging Noise

A banging noise or the sound of rattling from the indoor unit or outdoor condenser unit is often caused by loose parts. The indoor blower fan may have loose fan blades rattling around as the motor rotates the fan. Banging from the compressor is a sign of loose parts inside the compressor, such as a piston pin or connector rod, as well as parts on the outside of the compressor.

Fix the Noise

Call a professional to fix the banging noise right away, or further damage may be caused as your air conditioning unit continues to run. If loose parts repeatedly strike against others, banging noise and rattling sounds will worsen and more expensive service may be required to repair the air conditioner. If fan blades on the blower fan or outdoor fan are loose, they can often be reset. Loose parts inside the compressor typically mean the compressor needs to be replaced.

Clanking Sounds

Noises that sound like clanking could mean loose parts as well, but clanking noise may also tell you that the fan blades are not in balance. This issue can affect the indoor fan as well as the outdoor condenser fan unit. When the fan blades are not balanced, the blades hit against other parts as a cooling cycle runs. This causes damage to components and results in lower cooling system efficiency.

Fix the Noise

To fix the clanking sounds your air conditioner is making, turn off the system and call a professional to make repairs. Service will reposition the offending fan blades and help your air conditioner run more efficiently, using less electrical power each cycle.

Clicking Noise

If you’ve ever heard a fast clicking noise from your thermostat when the air conditioner first starts up and shuts down, this sound is normal. When a clicking noise repeats throughout a cooling cycle, it’s a sign of trouble. An electrical problem with a relay switch or capacitors in the compressor could cause the clicking noise you hear, or clicking is the sound of a dying thermostat that needs to be replaced.

Fix the Noise

Electrical issues within air conditioners can be difficult to identify, because there are so many electrical components within these systems. Have a technician come out to find and repair electrical malfunctions. It’s also wise to consult a professional before you replace the thermostat, just to make sure the issue cannot be corrected through repair. If you need a new one, your technician ensures your new thermostat is correctly installed and communicates effectively with your home’s air conditioner.

Buzzing Noises

If you hear buzzing noises from the air conditioning equipment outside your home, the sound could be caused by:

  • Faulty condenser fan – if the fan motor to the outdoor fan is going bad, it may produce a buzzing noise while it runs. Buzzing can also be caused by an electrical issue affecting the fan motor or debris inside the unit that are interfering with the condenser fan.
  • Faulty compressor – an electrical issue with the compressor can produce buzzing noises, such as a relay switch delivering incorrect amperage to the compressor.
  • Isolation feet issues – the compressor is installed upon rubber isolation feet, which can loosen or sustain damage over time. They may produce a buzzing sound as the compressor runs in this case.

If buzzing noises are heard from the indoor air conditioner, the problem is likely frozen evaporator coils. Buzzing noises can often be heard when ice has formed on the coils inside the central air system. Refrigerant leaks due to damaged refrigerant piping or a faulty expansion valve, or poor air circulation throughout the unit caused by a dirty air filter are issues that commonly cause evaporator coils to freeze up.

Fix the Noise

When buzzing sounds stem from issues within the outdoor air conditioner equipment, professional repair services are warranted to replace the compressor or repair damaged or loose parts.

When buzzing stems from frozen coils within the indoor unit, the system needs to be thawed:

  1. Switch the thermostat from COOL mode to OFF. Allow the air conditioner to rest and keep it turned off until all ice has melted.
  2. Switch the fan setting to ON instead of AUTO, which allows the blower fan to run around the clock to push warm air over the frozen coils, helping to melt the ice.
  3. Inspect the air filter. If it is dirty, replace it with a clean filter. A dirty filter is often to blame for a frozen air conditioning system.
  4. After all ice has melted from the coils, turn the thermostat back to COOL and the fan back to AUTO.

If your evaporator coils freeze up again, call a professional for repair services. Often, a fresh air filter solves this problem, but when freezing continues there is a more serious issue at play.

Squealing Noise

A high pitched squealing noise from inside the compressor should be fixed as soon as possible. Squealing is a sign of high internal pressure and dangerous operating conditions. You’ll hear the squealing sounds as the air conditioner first starts, and they last only about 10 to 15 seconds.

A less severe cause of squealing noise from an air conditioner is dry fan motor bearings or a loose fan belt. When bearings lose lubrication, they produce a squealing or grinding noise as metal rubs against metal within the fan motor. Older air conditioners use belt-driven blowers and condenser fan units, meaning a fan belt attaches to the fan and the motor. An old belt may become loose and slip from position, making a squealing sound as the system runs.

Fix the Noise

If you believe squealing is related to the system’s compressor, turn the unit off right away and request repair services as soon as possible to protect your compressor and air conditioning system.

Motor bearings are usually lubricated as part of your seasonal maintenance tune up. If you haven’t scheduled one this season, go ahead and do so now. If you would like to oil the bearings yourself, follow these steps:

Lubricate blower motor bearings

  1. Disconnect electrical power to the indoor unit.
  2. Detach the panel to access the blower compartment.
  3. Remove screws from the circuit board sitting in front of the blower assembly (if applicable) and move it to the side.
  4. Remove the bolts holding the blower assembly in place. Pull the blower assembly out from the compartment.
  5. Find the oil ports on the fan motor and remove their plugs.
  6. Insert two or three drops of light machine oil in each port. Replace plugs when finished.
  7. Reposition the blower assembly within the compartment and tighten bolts.
  8. Reposition the circuit board in front of the blower assembly and replace screws.
  9. Replace access panel to blower compartment.
  10. Restore electrical power to the unit.

Lubricate condenser fan motor bearings

  1. Shut off power to the outdoor condenser.
  2. Remove screws holding the condenser cover in place.
  3. Lift off the cover with attached fan assembly, or remove cover to access cage assembly within the condenser unit.
  4. Turn the fan assembly upside down to find the oil ports on the motor and remove plugs.
  5. Insert oil until ports are filled, wiping away excess oil before replacing port plugs.
  6. Reposition cage assembly (if applicable) and cover then reattach with screws.
  7. Restore power to the unit.

Reposition blower fan belt

  1. Cut electrical power supply to indoor equipment.
  2. Detach access panel to blower compartment.
  3. Guide the slipped fan belt back into position, looping around the motor pulleys.
  4. Test fan belt tension and adjust if needed. For deflection of ¾-inch or greater, make adjustments by loosening the nuts at the motor’s base.
  5. Reposition the motor unit to tighten the fan belt and tighten the nuts to hold the motor components in place once the fan belt is taut.
  6. Replace the access panel covering the blower compartment and restore power to the unit.

Hissing Noise

If you have an air conditioner making hissing noise, this is typically produced by a refrigerant leak somewhere within the system, either from the copper lines or a faulty component like a defective expansion valve. Refrigerant creates a hissing sound as it escapes cracks in refrigerant piping and elsewhere, because it is under great pressure when held inside the closed system.

Hissing can also be an early indicator of high internal pressure inside the compressor. A hissing noise will come before high pitched squealing.

Fix the Noise

A refrigerant leak requires professional repair, as technicians must possess an EPA license to handle refrigerant. The leak needs to be repaired and the system recharged with refrigerant so the air conditioner has adequate refrigerant to perform efficient cooling. If your home uses an older air conditioning unit, a refrigerant leak may allow harmful Freon to release into the atmosphere – newer air conditioners use environmentally friendly R-410A or Puron refrigerant.

Fix Air Conditioner Noises Fast

When your air conditioner noises aren’t resolved with the troubleshooting measures detailed above, it’s time to call Thomas & Galbraith for repair service. Our technicians are able to quickly diagnose and correct all causes of bothersome air conditioning noises and get your cooling system back to normal.

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