Not every noise your HVAC makes is a cause for alarm — but some are. Here's a guide to the sounds your system makes and what they mean.
Your HVAC system makes noise — that's normal. But there's a significant difference between the familiar hum of a healthy system and the sounds that indicate a problem. Knowing which is which can save you from an expensive emergency repair or help you catch a small issue before it becomes a big one.
Normal Sounds
- Steady hum: The normal operating sound of your compressor and blower motor. Consistent and relatively quiet.
- Click at startup and shutdown: Normal relay switching. One or two clicks when the system turns on or off is expected.
- Whooshing air: Normal airflow through ducts. May be more noticeable when the system first turns on.
- Occasional popping or ticking: Ductwork expanding and contracting with temperature changes. Usually harmless.
Sounds That Need Attention
Banging or clanking: Something is loose or broken inside the unit. Could be a loose part in the blower assembly, a broken motor mount, or debris in the system. Turn off the system and call us.
Squealing or screeching: Often indicates a worn blower belt (in older systems) or failing motor bearings. This will get worse over time and eventually lead to system failure.
Rattling: Could be loose panels, debris in the system, or — more seriously — a cracked heat exchanger in a furnace. The latter is a safety issue that requires immediate attention.
Clicking that continues after startup: Repeated clicking during operation often indicates a failing relay or control board. It can also indicate that the system is trying to start but failing — a sign of a failing capacitor or compressor.
Hissing: A hissing sound from your AC unit can indicate a refrigerant leak. You may also notice reduced cooling performance. This requires a professional diagnosis.
Bubbling or gurgling: Often indicates refrigerant issues or moisture in the system.
Loud banging at startup: In a furnace, this is often "delayed ignition" — gas builds up before igniting, causing a small explosion. This is a safety concern that should be addressed promptly.
When to Call Us
If you're hearing any of the "sounds that need attention" above, or if a familiar sound has changed significantly in character or volume, it's worth a call. On Time Home Services offers AC repair and furnace repair diagnostic visits throughout Temecula, Murrieta, and Southern California. Call us at (951) 277-6895.
