Why is my AC Making Loud Noises?

Ben Giesbrecht

Summers in Central California are uncomfortable enough with a properly functioning ac unit. Adding an irritating, loud noise from your air conditioning system can quickly send your stress levels through the roof!

Modern air conditioners are designed to be a lot quieter than units from 20+ years ago. If your HVAC system starts producing strange, loud noises, it's probably time to call a professional.

It is important to act quickly when loud noises start to come from your air conditioning unit because they could be symptoms of an underlying problem with the ac unit. Sometimes all you need is a thorough maintenance check from an HVAC technician (like the AC and Furnace tune-ups included in our Comfort Club membership). Other times, ignoring the loud noises in your HVAC system could lead to costly repairs and entire unit replacement.

The sooner you diagnose and troubleshoot the cause of the ac noises, the better your air conditioner's chances of providing you a long service life.

With that in mind, what types of noise could your air conditioning system produce? Below are some of the common causes of a noisy hvac system, and what they might mean. 

What noises might your air conditioning unit produce?

If you ever hear any of the following disturbing noises coming from your HVAC system, never ignore them!

AC Buzzing Noise

While hard to diagnose, an unusual noise like a buzzing noise might point to both minor and severe issues with your ac unit.

It could be an air filter needing replacement.

It might also be a sign of loose screws or parts within the cooling unit.

Sometimes the buzzing noise comes from the copper lines that run from outside to inside the unit. If a line is touching another surface, it causes a vibration.

Buzzing may be from the interior or exterior unit being clogged with junk.

The sound can also mean there is an unbalanced or loose blower fan, a dirty condenser coil, or a refrigerant leak.

Whatever the case, don't shrug it off. Be quick to call a professional and he will be able to diagnose your air conditioner noises.

AC Humming Noise

A humming sound coming from your air conditioning is not a serious cause for alarm. That said, it shouldn't be ignored either! It doesn't mean you have a severe air conditioner problem. In most cases, it is loose parts causing the noise. Usually, the refrigerant piping is a common culprit that sometimes gets loose and causes ac noise.

On the other hand, if the loose parts go unattended, you could be staring at bigger problems in the future. Another reason for humming noises is electrical issues, especially when a faulty compressor malfunctions or wiring gets loose.

AC Squealing Noise

An air conditioner making a squealing may mean the fan motors in your outdoor unit and the blower motors in your indoor unit are losing their efficiency. Squeals, screeches, and squeaks may also come from faulty blower wheels or malfunctioning blower housing.

Some air conditioner units make this noise as a typical running sound to some extent. You need to be able to tell what's normal and what's irregular in the squeals you hear.

AC Banging Noise

Banging sounds inside your AC are usually related to the unit's compressor. It might be that certain compressor parts like the crankshaft, piston pin, connecting rods, and others have come loose or completely broken. It could also mean the internal blower is out of balance.

If any compressor component breaks, you will probably need an entire compressor replacement.

AC Screaming Noise

If you hear high-pitched whistling or screaming, shut the air conditioner off and call an expert right away. The most likely cause is a refrigerant leak, which not only damages your air conditioner but can also threaten your family’s health. Screaming might also indicate high internal pressure within your compressor, which is very dangerous. If your ac turns off on its own, don't panic. Consider this a good thing. A sensor is doing its job to protect you from a potentially hazardous situation.

AC Pulsating Noise

An air conditioner making a pulsating sound isn’t necessarily a bad sign — a little pulsing noise can be perfectly normal when the air conditioner is operating. But if your outdoor A/C unit is making a pulsating noise that you can hear from inside the house, it could be a sign that something has come loose inside the unit and needs to be replaced. Some likely culprits include the fan motor and blades, but any loose panel or part could cause a pulsing noise in your AC. 

AC Cracking Sound

When the temperature is set too low, and the moisture is not draining correctly, or the fins are dirty, the coils in your HVAC unit’s evaporator can freeze. When ice falls from these coils, it makes a cracking sound that echoes through your system.

AC Clanking Noise

The common cause of a clanking sound in your unit is a loose or unbalanced part. These sounds usually come from broken internal components of the compressor. When loose parts such as internal fans are left unchecked, they will cause interference by constantly hitting other internal parts.

The longer you allow this to go on, the more damage it causes.

AC Hissing Noise

A hissing noise coming from your HVAC system is not something to be overlooked. Among the possible causes are leaky refrigerant lines, an internal valve leak, or a serious problem with your compressor. If the hissing noise is coming from your ducts, then you may have leaky air ducts. This is annoying, but not necessarily a cause for alarm.

Are hissing noises coming from the compressor?

The compressor can be found in the exterior air conditioning unit, which is also called a condenser. Listen around here for the hissing noise. If you find the compressor is the problem, this could be a hazardous situation because it is an indication that the pressure inside the compressor is too great. If you hear hissing, whistling, or shrieking coming from your compressor, turn off your air conditioner immediately and call an HVAC technician.

AC Rattling Noise 

Rattling sounds coming from your indoor or outdoor ac unit usually is a sign your ac is getting tired. After years of vibration and use, parts start to loosen and rattle. A good check over of bolts and screws in the unit's casing is a good start to finding the loud noise.

Twigs and leaves can also get clogged in your system. This means it's time for a cleaning.

AC Clicking Noise

If you hear an unusual, repetitive, clicking sound when your air conditioner turns on, this probably is an electrical problem that needs attention as soon as possible. Common causes of this are a failing thermostat or a defective control.

Electrical failures in ac units need to be dealt with right away in order to stop further problems.

AC Whirring Noise

If your ac has a persistent whirling noise, it is likely coming from the indoor blower or the outdoor unit. Usually, this is caused by a bad bearing or faulty fan in one of these components. A loose fan, broken fan, a bad belt, or a broken belt will cause a terrible whirring noise.

In a best-case scenario, the whirring from your air conditioner may be caused by a piece of paper or other debris that has been sucked into the indoor blower fan or the outdoor fan unit.

What do you do with a noisy AC?

While sometimes a noisy air conditioner may be beyond salvaging, in most cases, a simple repair or tune-up will do the trick and immediately restore your ac unit to factory-fresh running condition.

Talk to a Professional About Your Noisy Air Conditioner

Discussing your options with an AC repair expert will help you find the best solution for you. If you are in and around Atwater, Merced, Turlock, or Modesto, California, we will gladly help you. Exceptional customer service is our lifeblood, and we always strive to exceed your expectations.