AC Making Noise? Hissing, Buzzing, and Clanking Explained

A healthy air conditioner should run quietly in the background, making only the gentle "whoosh" of air moving through your vents. If your unit starts sounding like a jet engine, a bag of marbles, or an angry snake, something is wrong.

In the Antelope Valley, where our units run hard for 5-6 months straight, strange noises are often the first sign of a breakdown. Here is a guide to the most common AC noises and what they mean.

1. Hissing (The Angry Snake)

What it sounds like: A continuous hiss or whistle coming from the indoor or outdoor unit.

The Likely Culprit: Refrigerant Leak. This is the sound of high-pressure gas escaping the system. This is a serious issue that lowers efficiency and can freeze up your coils.

Urgency: High. Turn off your AC to prevent compressor damage and call a pro immediately.

2. Buzzing (The Electrical Hum)

What it sounds like: A loud, consistent electrical buzz or hum.

The Likely Culprit: Electrical Issues. It could be a failing capacitor, a stuck relay, or loose wiring. In Lancaster, heat and vibration often loosen electrical connections over time.

Urgency: Medium. If the fan isn't spinning but the unit is buzzing, turn it off to avoid burning out the compressor.

3. Clanking or Banging (The Metal-on-Metal)

What it sounds like: Loose metal parts hitting each other.

The Likely Culprit: Loose Parts. A fan blade might be out of balance and hitting the cage, or the compressor mounts might have come loose. Wind damage is a common cause of this in our area.

Urgency: High. A loose part can tear through copper lines or destroy the fan motor if left running.

4. Screeching or Squealing

The Likely Culprit: Fan Motor or Belt. On older units with belt-driven fans, the belt might be slipping. On modern units, it usually means the fan motor bearings are shot.

5. Clicking

The Likely Culprit: Thermostat or Relay. If you hear clicking but the unit won't turn on, it's likely a communication issue between the thermostat and the unit.