A healthy air conditioner runs with a steady, low hum. When it starts making a new noise, it's trying to tell you something, and ignoring it usually turns a small repair into a big one. Here's how to read the sound your San Antonio AC is making, and which noises mean shut it off now.
Hissing
A soft hiss usually means a refrigerant leak. Refrigerant is under pressure, and a leak makes a hissing or bubbling sound near the lines or indoor unit. You may also notice warm air and ice on the coil. A louder hiss or shriek can mean dangerously high pressure inside the compressor. Either way, this is a licensed-tech job, because refrigerant has to be handled by law.
Buzzing
Buzzing is almost always electrical. It can be a failing capacitor, a loose connection, a bad contactor, or debris in the outdoor fan. A buzzing outdoor unit where the fan isn't spinning is a classic failed capacitor. Electrical faults can escalate, so don't poke around inside a high-voltage unit. Turn it off and call.
Banging or clanking
A loud bang or clank means something is loose or broken inside, often in the compressor or the blower assembly. A loose part bouncing around can wreck everything around it. Shut the system off so it doesn't do more damage, and get it looked at before you run it again.
Screeching or squealing
A high-pitched squeal usually points to the blower motor or, on older units, a worn belt. Bearings going dry in the motor make this sound. It won't fix itself, and a seized motor can leave you with no airflow in the middle of a San Antonio August.
Clicking that won't stop
A single click when your AC turns on or off is normal. Constant clicking is not. It usually means a failing thermostat, a relay, or a control problem. It's often a smaller repair, but it'll only get worse, so catch it early.
Rattling
Rattling is often the easy one: loose screws, a panel that needs tightening, or twigs and leaves in the outdoor unit. Clear any debris from around the unit first. If it keeps rattling after that, a part is coming loose inside and needs attention.
Grinding
Grinding means metal on metal, usually motor bearings that have failed. This one's serious. Keep running it and you can burn out the motor entirely. Shut it down and call.
Which noises are emergencies?
Turn your system off and call right away if you hear:
- Loud banging or grinding (something is breaking)
- Electrical buzzing combined with a burning smell (fire and shock risk)
- A loud hiss or shriek (high-pressure refrigerant)
A burning smell with any noise means cut the power at the breaker and call now. Don't wait for morning.
The bottom line
Your AC's noises are a diagnosis you can hear. A hiss is not a buzz, and a rattle is not a grind. The sooner the right sound gets matched to the right fix, the cheaper and safer the repair. Most of these caught early are routine. Caught late, they take the whole system with them.
Call (210) 552-5850. We'll tell you what it actually is.
Matador Cooling and Heating is veteran-owned, licensed (TACLB134154E), and we run same-day and 24/7 emergency service across San Antonio. Tell us the sound, and we'll find the real problem, not just quiet it down for a week.
Schedule AC repair or call (210) 552-5850. If it's banging, grinding, or burning at 2 AM, that's exactly what our 24/7 emergency line is for.
Need it fixed today?
Veteran-owned, licensed, and available 24/7 across San Antonio. We find the real problem and tell you what it costs before we start.
Call (210) 552-5850