Every air conditioner makes some noise. You get used to the familiar hum of yours running on a summer afternoon. But a new sound, one you haven't heard before, is often your system trying to tell you something. Some of those sounds are harmless. A few mean turn it off right now. Here's how to translate what you're hearing, so you know whether to shrug it off or pick up the phone.
First, what's normal?
A few sounds are just your system doing its job: a low, steady hum while it's running, a single click when it turns on and again when it shuts off, and the soft whoosh of air through your vents. If that's what you're hearing, you're fine. It's when the sound changes, gets louder, or shows up out of nowhere that it's worth paying attention.
What do the different sounds mean?
Here's a rundown of the common ones and what's usually behind them.
- Buzzing. Most often electrical. A failing capacitor, a loose connection, or a worn contactor can all buzz, and so can loose parts vibrating or debris in the outdoor unit. Buzzing usually isn't an emergency, but it's a sign something is wearing out and worth having checked before it quits.
- Clicking that won't stop. A click when the system starts and stops is normal. Constant or rapid clicking is not, and it usually points to a failing relay, a control problem, or a thermostat issue.
- Screeching or squealing. A high-pitched squeal often means a motor bearing or a blower motor going bad, or a worn belt on older units. If the screech is coming from the outdoor unit and it's loud, that can signal dangerously high pressure inside. Shut it off and call.
- Grinding. Metal-on-metal grinding usually means a motor's bearings are failing. Don't keep running it. Catching it early can mean replacing a part instead of the whole motor.
- Banging or clanking. Something has come loose, a part inside the compressor or a fan blade hitting something. This one is a stop-and-shut-it-off, before the loose part does more damage.
- Rattling. Often the minor one on this list. Check for loose screws on the panels, or twigs and debris in the outdoor unit, first. If it keeps rattling after that, a part may be starting to deteriorate.
- Hissing or bubbling. Hissing can be refrigerant escaping from a leak, or air escaping from a leaky duct. A bubbling or gurgling sound also points to refrigerant. Refrigerant is licensed work and a leak needs to be found, so this one is a phone call to a licensed HVAC contractor.
- Whistling. Usually an airflow problem. Start with your filter, since a clogged one makes the system pull air through every gap it can find. Closed or blocked vents and leaky ductwork can whistle too.
Which noises mean turn it off right now?
If you hear grinding, banging, or a loud screech from the outdoor unit, or you smell anything burning, shut the system off at the thermostat and don't run it again until someone has looked at it. Running a machine that's grinding or banging is how a repairable problem turns into a replaced compressor or motor, which is the expensive end of this. When in doubt, off is the safe choice.
Which ones can I check myself?
A few are fair game before you call anyone:
- Whistling: change your filter and make sure your vents are open and unblocked. It sounds silly, but a lot of times we find that it's just the position of a vent that causes that sound.
- Rattling: tighten any loose panel screws and clear leaves or twigs out of the outdoor unit, with the power off.
- A soft hum: probably nothing at all.
Anything involving refrigerant, electrical parts, or a motor is where you want a professional, both because it's licensed work and because those are the parts you don't want to guess wrong on.
The short version
Your AC's normal soundtrack is a low hum, a click on and off, and air moving through the vents. New buzzing, clicking, or hissing is worth a call soon. Grinding, banging, a loud outdoor screech, or a burning smell means shut it off now. And a whistle usually just means it's time to change your filter.
If your system is making a noise you can't place, we can track it down. That's what our air conditioning service is for, and you can get on our schedule anytime. We're a family-run shop covering Nampa, Caldwell, Meridian, Boise, and beyond, at 208-455-5158.