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What Sounds Are Normal for an AC to Make?

Your AC unit makes some sounds when it cycles on, runs to cool your home, and cycles back off again. But what sounds are normal and which ones are cause for concern? It’s important to be aware of what’s normal for your AC so you can identify when a sound changes or the unit makes a new sound. Unusual sounds can mean that something is wrong with a component in your unit.

Most of the time you hear an unusual sound, something is in need of an expert eye to fix it. When you need Nashville AC repair, our team is here to help. You can know when to call by understanding these normal sounds your AC makes.

Compressor Hum

When your thermostat signals that it’s time to cool down your home, the compressor turns on. When it’s running, the compressor makes a humming sound that signals the motor is working. When you hear a slow, steady hum, you know that your compressor is working correctly to cycle refrigerant to cool the air and push it out through your vents. If you hear a hum and you’re not sure what it is, hold your hand up to a vent. You should feel cool air coming out as the compressor runs. If you don’t feel cool air, something may be wrong. Remember – not all problems produce an unusual sound.

Fan Blowing Air

Perhaps the loudest sound you’ll hear is the fan blowing air. This is because you can hear it through your entire home as the fan pushes air through the vents and into each room. While the fan is the loudest, it still isn’t a loud sound. It shouldn’t be distracting or cause for concern when you hear it. The sound of the fan shouldn’t disrupt what you’re doing. Instead, it is gentle and steady like the hum of the compressor. You might even call it white noise.

Water Flowing

Wait – water in your AC unit? Put down the red flags because the water flow is completely normal. Keep in mind that water flow isn’t constant, so you may not hear it every time your AC unit cycles on and off. Moisture condenses inside your unit as it filters out the humidity. This moisture doesn’t flow into your home. It collects in a drainage system and funnels out through the evaporator coil. So if you hear water, don’t be alarmed.

Ducts Rattling

The ducts that connect to your central HVAC are metal. When air flows through more forcefully, you may hear the metal rattle. This is especially common when the temperature is changing from hot to cold or cold to hot. The metal expands and contracts as the temperature changes. Keep in mind that this rattling shouldn’t last for long. If the sound persists, your metal ductwork may be loose.


At the end of a cooling cycle, your unit may click a few times as it cycles down. Just like ductwork rattling, the clicks shouldn’t last for long. The compressor and motor make clicking sounds when they stop, but if you hear clicking at any other time then it can be a problem. Paying attention to your AC cycle can help you understand if a sound like clicking is normal or not based on the timing.

Comfort is a must, call the experts you trust. Contact Precision Air, Inc today for your HVAC and indoor air quality needs. 

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