10 Strange A/C Noises and What They Mean

June 13, 2017

Curious about that strange sound coming from your A/C?

Unfortunately, a strange noise usually means something’s not working correctly with your system and may require the air conditioner to be repaired or even an replacement. 

In this article, we’ll cover 10 different A/C sounds and what they mean:

  1. Banging

  2. Clanging

  3. Bubbling/gurgling noise

  4. Screeching

  5. Squealing

  6. Clicking

  7. Buzzing

  8. Humming

  9. Slamming

  10. Whistling

Let’s start with #1, a banging sound...

10 strange A/C noises: What they mean and how to fix them

#1: Banging

What causes the noise: A banging sound usually is a sign that there’s a loose component inside your compressor, like a connecting rod, piston pin or crankshaft. Additionally, a banging noise could mean you need a new compressor.

Solution: Contact a professional to inspect your air conditioner’s compressor for any loose parts.

#2: Clanking

What causes the noise: Clanking could mean you have a loose part, possibly the compressor itself. This sound can also mean that the indoor blower and outdoor fan blades are out of balance. If you ignore this clanking sound, it will only get worse with time.

Solution: Contact an A/C expert to check for loose parts and make sure your blower and outdoor fan are working properly.

#3: Bubbling/gurgling

What causes the noise: You may have a hard time knowing where the bubbling/gurgling sound is coming from, but it’s most likely related to a refrigerant leak. A gurgling sound could also mean that your condensate drain line is clogged.

Solution: Call a professional to check your A/C for a refrigerant leak and to make sure your condensate drain line trap is clear of blockage.

Read our article 5 Signs Your Home’s A/C is Low on Refrigerant for more info on how to detect refrigerant leaks.

#4: Screeching

What causes the noise: If you hear a very loud screeching noise, like metal on metal, when you turn your A/C on, it likely means that the fan motor bearings are worn out.

Solution: You’ll need to have your fan motor replaced by a professional if you hear this screeching sound.

#5: Squealing

What causes the noise: Intermittent or constant squealing points to a misaligned or worn fan belt. The sound can sometimes come and go depending on temperature and humidity levels, which makes the belt expand and contract. If you don’t replace a worn fan belt, it will eventually break, so you run the risk of not having air.

Solution: Contact an A/C technician to replace your fan belt.

#6: Clicking

What causes the noise: Let’s look at 2 different clicking noise scenarios:

1. Clicking while the A/C is running: If you gradually hear clicking coming from your outdoor unit, there’s probably a small object obstructing your unit’s fan.

Solution: Turn off your A/C and check to see your outdoor unit to see if anything is blocking the fan. Remove any objects that obstruct the fan blades.

2. Clicking when your A/C won’t start: This type of clicking means there’s an electrical problem. The problem could be with the thermostat, compressor or capacitor.

Solution: Contact a professional to inspect your A/C’s electrical system.

#7: Buzzing

What causes the noise: A buzzing noise also indicates that there’s an electrical problem with your air conditioning system. The electrical problem could be caused by a faulty relay switch, circuit breaker or condenser fan motor.

Solution: Contact an A/C technician to inspect your A/C’s electrical system.

#8: Humming

What causes the noise: Humming usually means your air conditioner has an electrical problem, similar to what causes a buzzing sound. Humming can also indicate there are loose wires/hardware, or a blower motor issue.

Solution: Contact an A/C technician to check for any loose wires hardware and to make sure your blower motor is running smoothly.

#9: Slamming

What causes the noise: If you hear a slamming noise, especially when you turn off your A/C, it could be caused by a variety of issues:

  • An air filter that’s slamming against the return grille

  • A closing damper

  • Expanding & contracting ducts

  • Blower motor fan problem

  • Outdoor compressor’s internal support springs are busted

  • The outdoor fan is knocking against the unit

Solution: Contact an A/C technician to check your air conditioning unit for these issues.

#10: Whistling

What causes the noise: A whistling noise is a sign of low airflow, which is caused by...

  • A dirty air filter

  • Blocked return vents

  • Closed dampers

  • Leaky ducts

  • A malfunctioning blower

Solution: Try changing your dirty air filter and making sure nothing is blocking your return vents. If that doesn’t fix the whistling sound, contact an A/C professional to look into the problem.

Hearing a strange noise from your A/C? Let a professional help

If you hear any of these 10 sounds, contact Red Cap Air to schedule an air conditioning repair. We’ll send one of our trusted technicians to your home to stop that annoying sound so you can have some peace and quiet while you stay cool.


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