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What Are the Normal Sounds From an AC?

relaxed-womanAir conditioning systems don’t yet have a way to self-diagnose malfunctions and clearly communicate them to homeowners. (Although we have no doubt this technology will emerge in the future.) Instead, homeowners have to know the various warning signs of an AC that’s struggling. One of the most common warnings is an odd noise. We’ve written before about some of these AC strange sounds to listen for

You can approach warning sounds from the other side as well: what sounds should you expect to hear from your AC when it’s running in good condition? In this post we’ll go over the standard noises an AC makes to give you a better sense of when something sounds wrong so you can act on it and call us for air conditioning repair in Tampa, FL!

Blowing air

This is the basic sound you hear from a central air conditioning system when you’re indoors. It’s the noise of the blower fan in the HVAC system drawing air through the return ducts and blowing it across the evaporator coil of the AC and through the ductwork. Innovations in blower motors have made the sound of this fan quieter than ever before, so this is a sound you’ll soon tune out during the summer. (If it gets abruptly noticeable, something may be amiss.)

Hum of the compressor

When the cooling cycle of an air conditioning system starts, the compressor activates with a slight thunk followed by a steady whir. It sounds like a second, deep-toned fan over the sound of the main fan. You’ll probably only notice this noise if you’re outside and near the condenser cabinet. The compressor hum should last for 10 to 15 minutes at a time before cycling down. Watch out for longer or shorter cycling times, as this can indicate a malfunction. If you hear the compressor working but don’t feel any cool air from the vents, this is also something that needs investigating.


Periodically, you’ll hear the sound of water dripping and sloshing from the interior of the AC cabinet. This is the movement of condensate moisture out of the air conditioner. This moisture gathers along the evaporator coil as the AC cools the air, a side-effect of refrigerant evaporation. The water moisture drips down into a pan and then exits via a drain to the outside. 


If you’ve read about the warning sounds from an AC, then you might have seen “clicking” on the list. But clicking is also part of the standard air conditioner noises—you just have to know when to expect to hear it. When the AC shuts down, both compressor and fan, you’ll probably hear some brief clicking coming from the cabinets. This is the noise of mechanical components powering down, and it’s similar to what you hear from a car engine when it shuts off. Clicking sounds that occur at startup, are too loud, or happen continuously are a cause for concern, however.

When in doubt about the sounds from your AC, give us a call!

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