The newer your A/C system, the quieter it is. That means when it does make a noise, it’s all the more concerning.
Though the noise is likely from a minor issue, those minor issues can be big problems if you ignore them.
6 A/C Sounds You Shouldn’t Ignore
Here are some common noises you may hear from your unit and what they might mean.
1. Clanking or Banging. Both of these noises could indicate a loose or broken piece from inside the A/C compressor,
like a connecting rod, crankshaft, or piston pin. It could also mean your system needs a compressor replacement or that
your indoor blower is unbalanced.
2. Clicking. There’s a normal clicking sound of the electrical components at the start or shutdown of any air conditioning
system. Constant or ongoing clicking, however, may be a sign of a failing thermostat or defective control. Any electrical
issue could be a big deal, so if you hear clicking that isn’t typical of your system, it’s best to get a check from a
3. Squealing. When outdoor fan motors and indoor blower motors squeal, it may be a sign that they are about to go
bad. Likewise, when the blower wheel and housing wheel malfunction, they often squeak, rattle, or squeal.
4. Humming. Most A/C units will hum when running, but if it’s a new sound, it may be a signal that something is off.
Usually, a hum isn’t a serious issue. It could mean loose parts or issues with refrigerant piping. A compressor that hums
but doesn’t start may indicate a problem with the motor or loose wiring.
5. Buzzing. If you have a buzzing noise coming from your A/C unit, it could mean a few different things:
• Debris in the outdoor unit.
• Debris in the indoor unit.
• A loose outdoor fan motor.
• The condenser coil is dirty.
• Loose or out of balance fan blades.
• Cooper lines rubbing against something.
• A dirty air filter.
• Leaking refrigerant.
6. Rattling. Rattling may mean the deterioration of some of your system’s parts, but it could also mean something as
simple as debris clogging your system. Sometimes, an electrical contractor inside the system will make a chattering
sound. If fans are loose, they also make a rattling sound. If you hear a rattle, look for loose screws in the casing, clean
the condenser coils, and change your filter.
When to Call a Pro
Most noises don’t necessitate an immediate call, but, if your system is making a high-pitched scream or whistle, turn it
off and call us right away. That sound could indicate a refrigerant leak that could damage both your health and the
Regardless of what sound your A/C unit makes, if it’s a new one, it probably needs a professional eye – or ear – to
diagnose the issue. To ensure the safety of your system, it’s best to turn it off until talking with a professional. Small
problems can turn into big ones without the proper diagnosis. Sometimes a phone call is all you need!