ABC Blog

Why Is My AC So Loud?

an AC vent

Air conditioners can make our homes comfortable, especially on hot and humid days. But that comfort can be minimized when you find yourself asking, “Why is my AC so loud?” If you notice whistling, banging or rattling sounds coming from your AC, it’s probably time for a tune-up. It can also be your AC’s way of telling you that there’s a more severe issue and that you should call a professional.

If your AC is disturbing your peace at home, here are the possible reasons for its loud noises. While there are some home fixes you can try, the best way to deal with the issue is to leave it in the hands of capable HVAC specialists. They will assess your AC thoroughly and provide the best possible solution.

Here are the most common types of AC noises and what they mean.

Banging or Clanking

If your AC is making banging noises, that’s usually a sign that the compressor is worn-down and needs replacing. Over time, compressor parts like the connecting rod, crankshaft and piston pin can break or become loose and bang around. Banging noises can also mean your AC’s indoor blower is unbalanced, loose or dirty and is striking the sides of the housing unit. HVAC specialists will usually fasten or replace these loose or broken parts.


You’re probably used to your AC making clicking sounds when you turn it on and off. While that’s normal, there can be an underlying problem if the sound persists the whole time your AC is on. It can be a sign of malfunctioning electrical signals, a loose or blocked fan, insufficient charge in the capacitor or a faulty thermostat. If you’re hearing a constant clicking sound, don’t ignore it because it can cause a system failure.

Squeaking or Squealing

If your AC makes a squeaking or squealing sound through its duct system, it’s a possible sign of a faulty blower or fan. Indoor blowers and outdoor fan motors squeal loudly to let you know they are on their last leg and need a replacement. Some air conditioners make a squealing sound when you first turn them on. If your unit has always been that way, it’s probably normal. But if the squealing is a new sound, it’s best to contact a professional to diagnose the problem.

Rattling or Chattering

If your AC is rattling or chattering, a foreign object or a loose part might be the culprit. Look for any twigs or debris that are obstructing the system. Also, check if there are any bolts or screws that need tightening. If these fixes don’t stop the rattling noise, it can be a sign that your unit’s electrical contractor is about to give up. Contact an HVAC specialist to prevent any further damage.


While a humming air conditioner isn’t usually a cause for alarm, it’s still a sign that there’s something off with your unit. Check if the refrigerant pipe is causing the vibration or if any loose parts are hitting the housing unit. While it is probably nothing too serious, it is worth getting the opinion of an HVAC specialist. That way, it doesn’t escalate into a bigger and more expensive problem.


If your AC is making a high-pitched whistling sound, turn it off. Several factors could result in this noise. Keep reading to find out why your AC might be whistling and how to fix this issue.┬áIf your AC shuts off amid the whistling, that’s the sensor’s doing. That’s your cue to call the professionals so they can fix the issue.

a thermostat

Can I Replace My Thermostat Myself?

There are many possible reasons for a loud AC, and a thermostat that’s not working is one of them. While it can be tempting to replace the thermostat yourself to save money, it is not the best idea. Installing a thermostat isn’t a DIY project you can do for fun on the weekend. It is a challenging task that comes with several risks. Here is why you should leave thermostat installation to the pros.

They Come With Complex Wiring Systems

Thermostats have developed significantly throughout the years. They are no longer the simple devices of the past. The new design comes with complex wiring systems that require the knowledge and expertise of an HVAC professional. If you attempt to configure it yourself, you could damage the thermostat and spend more money than intended.

They Have Advanced Features

Aside from having complex wiring, new thermostats boast various advanced features. You can connect them to your dual-fuel heat pumps, whole-home humidifiers, zoned HVAC systems and Wi-Fi networks. But these require separate configurations. In addition, your HVAC system might require additional rewiring to be compatible with the thermostat.

You Will Void Your Warranty

Most thermostat manufacturers will void your warranty if you perform the installation yourself. It’s their way of protecting themselves against user negligence. If you want to preserve your warranty’s validity, let an HVAC technician configure your thermostat. That way, you’re covered if it malfunctions in the future.

You Might Hamper the System’s Efficiency

Thermostats function the best when installed professionally. Otherwise, they tend to be less cost-efficient. If you have a solar-powered generator at home, a poor thermostat configuration can put your savings to waste. While the DIY approach might sound less costly, that is seldom the case.

For these reasons, it’s best to contact an HVAC expert to install your thermostat. There are several ways to know if you need to replace your current one. These include constant temperature swings, incorrect temperature readings, an unresponsive AC system and higher electricity bills.

a home with an air conditioner that is making a high pitched whistle

What to Do When Your Air Conditioner Has a High-Pitched Whistle

A whistling AC is never a good sign. The most common reason behind the alarming sound is insufficient airflow in the ductwork and return vents. If that is the case, your AC has to work harder to move air through its system. That causes high-speed and high-pressure air to travel through the return vents, creating the whistling sound you hear. Here are some things that can lead to poor airflow.

Dirty Air Filter

A dirty air filter can slow down the airflow in the central air system. Professionals recommend replacing your air filter every three months or when it is visibly dirty. Make sure you install the correct air filter type and size.

Duct Leaks

The ductwork in your home consists of several joints. The sealing between these joints should be airtight for the system to work efficiently. Over time, the seals can develop holes and leaks. That allows air to escape, creating a high-pitched whistling sound.

Improper Ductwork Configuration

It takes a lot of engineering and planning to get ductwork right. Technicians have to balance the amount of airflow with the blower’s capacity. If the system in your home has a faulty design or has changed over time with new equipment installations, that can result in an airflow imbalance marked by a whistling sound.

Closed Vent Dampers

Vent dampers are handy if you don’t want air to flow into unused rooms in your home. However, ACs generally work best if all vent dampers are open. If your AC has been whistling, check if your vent dampers are closed and obstructing the airflow.

Blocked Vents

It is easy to cover the vents in your home without knowing it. If boxes, furniture, curtains or other objects are blocking them, that could be the culprit behind the poor airflow and whistling sound. Clear the space around your vents and see if that solves the problem.

Closed Doors

If you have several rooms in your home, leave some doors open to improve airflow. Even though house doors aren’t airtight, your AC has to pull air through small gaps, causing it to overwork and whistle.

If you have a whistling AC in your home, it is a warning sign that you shouldn’t ignore. Instead of trying to diagnose and fix the problem yourself, contact HVAC specialists. They are the experts for a reason. They can pinpoint the root of the problem and provide safe, effective and long-term solutions.

The Bottom Line

A loud AC isn’t just a disturbance to the peace in your home. It also marks the beginning of your AC’s deterioration. Contact HVAC technicians immediately if your AC is whistling, banging, clicking, or making other sounds. That way, you have skilled professionals to address the problem before it worsens, preventing more expensive repairs in the future. They will come to your home at your convenience and return your AC to its quiet and efficient state.

ABC Can Keep Your AC Working Efficiently

Dealing with AC issues requires lots of technical know-how. Instead of trying to figure it out yourself, contact ABC Home & Commercial Services. Our professionals can efficiently diagnose and repair your AC problem. They can also offer advice on when to replace your air conditioner.

Tom Riggs

Tom Riggs is the Division Manager for Mechanical Services, overseeing sales and operations for HVAC, Plumbing, Electrical, Appliance Repair and Water Quality for all ABC Austin branches. He joined ABC in 2014. Before ABC, he was an HVAC Service Technician, HVAC Comfort Advisor/Sales and Operations Manager. Tom attended Universal Technical Institute. He's an avid outdoorsman and enjoys country living with his wife and two sons.

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