AC is Making Noise

What to Do When Your AC Is Making Noise

Air conditioning units have evolved since their days as loud, rattling machines that people tolerated in the name of staying cool. After all, Texas’ average high of 94 degrees in July and low of 74 degrees doesn’t give people much choice.

But thankfully, that’s all changed. Today’s units are nearly silent. If you already have an AC unit (and you probably do) chances are you can’t even tell when it’s running.

In fact, many modern AC units measure under 50 decibels. For reference that’s quieter than light traffic and comparable to a babbling brook. So if you can clearly hear your AC unit there’s most likely something wrong.

Hissing, buzzing, rattling, thumping, and banging all indicate problems with your unit. And with Texas’ high temperatures and the cost of a new air conditioning unit you shouldn’t take any chances.

So today, we’re breaking down what to do when your AC is making noise. We’ll take a look at what each noise means and how to fix them.

But First, Let’s Talk Cost

Noise coming from your AC unit usually means either a repair (at best) or at worst a brand new unit. While you might get lucky and only need a repair, the average repair still costs $337 and can range into the thousands of dollars.

What’s more, if you ignore the noise for too long an entirely new unit prices skyrocket.

Installing a standard air conditioning system costs, on average, $5,358, with costs ranging from $3,730 – $7,178. Depending on the area an installation can cost up to $10,278. Assuming a $60,000 per year salary that’s well more than a week’s pay.

The costs alone make ignoring strange AC noises a costly mistake.

Banging and Thumping

While banging and thumping seem like serious noises they’re actually some of the better AC sounds because you’ll definitely hear them. Other sounds on this list can go unnoticed and cause unfixable damage.

If you’re hearing a bang or thump chances are there’s a loose or broken part inside your AC unit. Blower fans knocking against the unit are a common culprit but any loose part can cause a similar noise.

Run your system with the fan turned off. If the banging stops it’s the fan, and if it continues you’ll need someone to open the unit to find the cause.

Sometimes banging and thumping from units located outside the home comes from a stick or other debris stuck in the fan. In this case, so long as there’s no fan damage you’ll only need to remove the debris.


A clicking noise coming from your AC system is often far more subtle than banging and thumping. In fact, homeowners commonly attribute the noise to another appliance. If you hear continued clicking when the AC turns on or off, don’t ignore the noise.

Clicking indicates there’s something wrong with either a contractor, relay, thermostat or other electrical components. Finding the culprit means opening the machine and testing for current, looking for frayed wires, etc.

Occasionally, outdoor units click if there’s something stuck in the fan. Though this happens when the AC is running, not only when it’s turning on or off.


High pitched screaming or whistling is the worst noise you can hear. The sound comes from a broken compressor and is usually heard at startup. A faulty compressor not only means the unit won’t cool air but that it could leak refrigerant.

The refrigerant is toxic both in the air and to the touch, meaning even the smallest leak can cause health problems. If you think there’s a compressor issue or see visible refrigerant shut the unit down immediately.

With any luck, the sound is coming from the compressor motor and not from dangerous internal pressure inside the compressor itself.


Like clicking, buzzing usually indicates there’s something wrong with your AC unit’s electrical components. The buzzing usually comes from one of the following issues:

AC Condenser Fan Motor: The condenser fan motor is a large fan located inside your condenser that keeps the AC unit cool as it converts refrigerant from a gas to a liquid. If the motor that turns the fan malfunctions it can start buzzing, and continue buzzing while the AC runs.

Contactor Relay Switch: The contractor is what allows electricity to flow and power the high-voltage parts of your AC unit, like the motors and compressors. A bad contractor often buzzes when the switch isn’t opening and letting the electricity through.

Circuit Breakers: Circuit breakers “trip” when they’re overloaded, protecting your AC system from pulling in more electricity than it’s designed to withstand. And while tripped breakers aren’t an issue, dirty or shorted breakers commonly buzz.

Loose Wiring: Wiring can come loose over time, leading to bad connectors that sometimes make a buzzing noise. Of all the problems that cause buzzing, a loose wiring is the easiest fix.


Rattling is probably the best of all the AC sounds we’ve discussed so far. In general, a rattling noise just means there’s something loose in your unit. Any number of components can come loose over years of use, so opening the unit is the only real way to find the cause.

Though sometimes loose screws, nuts, and bolts on the unit’s exterior can cause rattling noises. All in all, if your unit’s rattling it’s probably not too pressing.

If Your AC Is Making Noise, Call a Professional

Barring a loose screw on your AC unit’s casing, when your AC is making noise it’s best to call a professional. Most problems are too complicated for the average homeowner, not to mention that you won’t find replacement parts at Home Depot.

When fixes range from simple to dangerous it’s better to use caution and let a repair service help you keep cool.

So if you’re in the market for an air conditioning service, get in contact with us. Our team of experts can help keep you cool without breaking the bank. We know AC, and want to help you whenever we can.


Is your air conditioner hissing, buzzing, thumping, or making other questionable noises?  Call Chill Air, a top air conditioner repair company in Richardson, TX, at  (972) 699-8080 today to schedule a time to have your AC unit serviced! 


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Chill Air ConceptTop-rated, professional commercial & residential AC, heating & refrigeration company serving North Dallas, Texas since 2000. Licensed, Bonded & Insured contractor – We repair and service all HVAC brands, makes & models. Call (972) 699-8080 or send us a message here to schedule your appointment with us.