Strange AC Noises and What They Mean

When you have your AC running, the last thing you want to hear is the system itself. Over the years, AC systems have become quieter and quieter; that’s why it’s alarming when you hear some odd noises coming from your AC unit. Some noises are normal, and even expected. When you start your AC for the first time after a season of laying dormant, it’s natural to hear some rattling as the system comes to life; what’s not normal is if those noises last. For the care and keeping of your HVAC system, we’re sharing strange AC noises and what they mean.


If you hear a banging sound coming from your AC system, chances are that something is broken. Banging sounds can come from a connecting rod, piston pin, or crankshaft; these pieces could be broken or completely loose. Another reason you may hear banging from your AC unit is if a stick or some other debris is stuck in your condenser. Either way, it’s best to turn off the AC when you hear banging. Call an HVAC professional so they can diagnose and fix the problem.

Screaming or Screeching

We all know the noise, a mechanical wailing coming from your HVAC system. It’s not a pleasant AC noise and should be investigated immediately. When a screaming noise is coming from your AC unit it could mean a few things. It could mean there’s a refrigerant leak in your system. If this is the case, turn off your AC immediately because a leak will damage your AC system and has the potential to hurt you or your family members. Another cause of a screaming AC could be high pressure buildup in the system. This buildup can cause the compressor to release a screaming or screeching noise. If you hear this, turn off the system immediately and call an HVAC professional ASAP.


If you hear a clicking noise, it could mean a few things. The easiest to deal with is loose debris in your compressor. If you think there’s something interfering with the fan in your condenser, turn off the unit and see if you can remove it yourself. If not, call an HVAC professional to tune-up and clean the unit. The harder issue could be electric. Sometimes, if the electric is old or frayed, it could cause a clicking noise.

Humming or Buzzing

Humming or buzzing noises can be some of the most annoying AC sounds, but they should never be ignored. Buzzing can mean a lot of things, from a failing compressor to damaged condenser feet. If you hear a buzzing it could even mean your AC unit has frozen over; or it could mean that there are some loose parts rattling around. While you can keep your AC unit running with some buzzing, call an HVAC technician to diagnose and fix the problem.


Squealing is not a pleasant noise. It can even hurt your ears. We all know cars can squeal, but what about your AC? Yes, your AC can make a loud squealing noise, and when you hear it, don’t push it aside or ignore it. Often, squeals can indicate that a belt is lose and needs to be replaced or readjusted. Also, belts can also expand, and contract based on outdoor temperature, potentially exacerbating the already terrible AC noise.

Hearing Some AC Noises? Call Service Champions

Keeping your AC unit in tip top shape is what we do. At Service Champions Plumbing, Heating & AC our techs are expertly trained every year to keep up with new systems and new technology. We are the only Diamond Certified Plumbing and HVAC company serving Orange, Riverside, and Los Angeles counties. To schedule some of our stellar service, reach out to our call center representatives or click here to schedule an appointment online.