Is your HVAC system making loud or strange noises? What strange HVAC sounds mean and when to call a St. Louis expert.
If your HVAC system is making more noise than usual, it’s trying to tell you something—and it’s not just complaining about the St. Louis humidity. Whether it’s a rattle, hum, bang, or buzz, loud HVAC noises can signal anything from minor to serious mechanical problems.
Don’t tune it out! Recognizing the sounds and their causes can prevent costly repairs, extend the life of your system, and keep your home safe and comfortable.
The technician Giovanni was excellent and on time very professional and efficient and knowledgeable of the project at hand ,gave great advice but most of all did great work 👏 thank you .
Your service technician was very professional and knowledgeable. And did not appear to try to give me bogus information. I truly appreciate his honesty because several other companies did not appear to be honest, obviously wasn’t honest, my gut feeling told me they were not honest and tried to get me to spend $10,000 for a problem that was much simpler to fix. I look forward to you servicing all my properties, and possibly those of the rest of my family.
Response from the owner:Thank you so much for the kind words and great review! We appreciate your support.
Very prompt, communication was great, and the workers were very polite. I highly recommend them!
Response from the owner:Thank you, Lianne! We're glad to hear that you had a positive experience with our team and appreciate your high recommendation.
Water heater repaired, appointment done the same day, effective, courteous
Response from the owner:Thank you, Leticia! We appreciate your kind words and are glad to hear that the water heater was repaired promptly and effectively. Your satisfaction means a lot to us!
Response from the owner:Thank you, Hank, for your wonderful feedback; we're glad you enjoyed the fast, friendly, and professional service, and we'll be sure to keep up the great work!
The service tech Giovanni did a fantastic job. Our gas fireplace is working like new again so we’re ready for the cold weather!
Response from the owner:Thank you, Mr, for your fantastic review! We're glad to hear Giovanni provided you with excellent service and professionalism. Your recommendation means a lot to us!
⭐️⭐️⭐️⭐️⭐️ If I could give 10 stars, I absolutely would.
Last night our furnace went out unexpectedly, and with three kids in the house, the temperature dropped fast. Giovanni went above and beyond in every way possible. Instead of charging me a late-night service fee, he simply asked, “Are you decently handy?” and offered to walk me through some troubleshooting steps to get our heat back on so my children wouldn’t have to sleep in the cold.
Not only did he guide me through the process, he even FaceTimed me and showed me exactly what to take apart, how to put it back together, and what signals to watch for. It felt like having a real technician standing right next to me the entire time. Thanks to him, our heat was restored within minutes.
In a world where true customer service is hard to come by, Giovanni is a rare find. It is a guaranteed fact that any future repairs, maintenance, and the new heater/AC system we’ll be needing this coming summer/fall will absolutely be done through him. His honesty, kindness, and expertise have earned our business for life.
Highly, highly recommend.
Response from the owner:Thank you, Jeff, for sharing your experience! We're so glad to hear Giovanni was able to help you and your family during that tough situation. Your recommendation means a lot to us, and we appreciate your trust in our services for the future!
My neighbor referred these guys to me when had water heater problem. Previous company told me I needed to replace it. Tom’s technician fixed it for less than $200. This was over 2 years ago and have been using their service ever since. They are very trustworthy.
Response from the owner:Thank you, Mary, for sharing your experience and for trusting us with your water heater issue; we're glad our technician could help and that you've continued to rely on our services!
I called this company earlier today because I was having a bunch of issues with my HVAC system. They were incredibly friendly and walked me through troubleshooting step by step over the phone. They didn’t even charge me for the call. Thanks to their honest advice, I was able to get things running smoothly again. Really grateful for their help and would definitely recommend them if you want straightforward and trustworthy service. Five stars all the way!
Response from the owner:Thank you so much for the glowing review, Hector! We appreciate your business and look forward to working with you in the future.
Nick did not set current time. — Monday Hoffmans Zach came to fix correct time. We DID NOT want a timed thermostat — we prefer to set temperatures manually
Response from the owner:Thank you, Pat, for your kind words about Giovanni; we appreciate your feedback and are glad to hear that he made a positive impression.
Clear communication about arrival, service and costs.
Response from the owner:Thank you, Margaret, for your kind words! We appreciate your feedback on our clear communication and are glad you had a positive experience.
I will highly recommend this business for your air and heater repair. Prompt, knowledgeable and courteous service.
Response from the owner:Thank you, Judy, for your kind words and recommendation! We're glad to hear you were pleased with our prompt and courteous service.
Thomas Hoffman was very responsive to our after hours inquiry, even walked us through some trouble shooting over the phone. We provided pictures of the unit and they were able to quickly buy, schedule and install the part to keep our family warm!
Response from the owner:Thank you, Ali! We're glad to hear that Thomas was responsive and helpful in getting everything sorted out for you and your family. Your feedback means a lot to us!
Nick came by, identified the problem quickly and had it fixed. Great service!
Response from the owner:Thank you, Ted! We're glad to hear that Nick provided you with quick and effective service. Your feedback is greatly appreciated!
Great service. Responsive. Well trained technicians. Honest friendly and thorough. I highly recommend Tom Hoffmann and his team.
Response from the owner:Thank you for your kind words! We appreciate your recommendation and are delighted to hear about your positive experience with our team.
Ryan Taylor with Thomas Hoffman did an outstanding job in servicing our unit & explaining everything to me, especially how our humidifier worked, since we were new home owners & had not had one before. Thank you!
Response from the owner:Thank you! We're glad to hear that Ryan and Thomas provided you with excellent service and helped you understand your new humidifier. We appreciate your feedback!
As always, the Hoffmann technician Zach was polite, professional, and efficient. Pricing is reasonable and even more importantly, they are dependable. I will continue to use Thomas Hoffman A/C and Heating.
Response from the owner:Thank you, Mark, for your kind words about our technician and for your continued trust in Thomas Hoffman A/C and Heating; we truly appreciate your support!
Response from the owner:Thank you, Brandon! We appreciate your kind words and are glad to hear about your positive experience with Hoffmann’s professionalism and thoroughness.
Our service technician arrived right on time and was professional, friendly, efficient and courteous. We couldn’t ask for more.
Response from the owner:Thank you for sharing your positive experience with our service technician! We appreciate your kind words and are glad to hear that you were satisfied with the service provided.
I'm a new customer and had my first appointment for furnace check.My tech was Zack and what a professional. He explained how he checked system and answered all my questions. This was a very good experience
Response from the owner:Thank you, Patricia, for your kind words! We're glad to hear that Zack provided you with a professional and informative experience during your furnace check. Your satisfaction means a lot to us!
Thomas Hoffman is a wonderful company to work with. Techs are knowledgeable, personable & efficient.
Response from the owner:Thank you, Christine, for your kind words about our team; we appreciate your feedback and are glad to hear you had a positive experience!
I called on December 25th at midnight and started leaving a message and Thomas Hoffman the owner called me back almost immediately. He said he would come out the next morning between 8:00 and 10:00 am snd he was promptly on time. He fixed my problem and while he was there I decided to get an estimate for a new furnace and air conditioning unit. The price was very reasonable and the installers one of them being his son were both very professional very courteous, polite, arrived on time and finished the same day. I enjoy knowing that I now have the support of Thomas Hoffman heating and air conditioning along with the peace of mind that comes with owning a Trane. Nothing stops a Trane.
Albert Koesterer
Response from the owner:Albert thanks so much for your kind reviews and your business. We truly appreciate it!!!
The Thomas Hoffmann team did a great job taking care of our semi annual HVAC maintenance. They not only worked with us to schedule the visit, but also did an excellent job sending us reminders on when they would be out.
Response from the owner:Thank you so much for the great review, Bob! We appreciate your support and are happy to hear you had a great experience!
Nick was excellent. Super profession, quick, and up front with the pricing (which was fair). Hopefully we don't need to call anyone to fix our AC again, but if we do - I'm calling Nick!
Response from the owner:Thank you, Layton, for your amazing review! We really appreciate your support and hope to be your first call for any future repairs!
Is It Normal for HVAC Systems to Make Noise?
Some low-level noise is normal, like the soft hum of the blower fan or a brief click when the system turns on. But sudden, loud, or persistent noises usually indicate a problem.
Common causes include:
Loose parts
Poor maintenance
Dirty filters or coils
Failing motors or compressors
Ductwork issues
Let’s break it down by noise type.
1. Banging or Clanking
🔊 What it sounds like: Metal-on-metal hitting or thudding ⚠️ Likely cause: A loose or broken part banging inside the unit, like a connecting rod, piston, or blower motor component.
Why it matters: This can cause severe internal damage if ignored.
🛠️ What to do: Shut off your system and call a technician immediately.
2. Buzzing or Humming
🔊 What it sounds like: A steady, electrical-sounding hum or buzz ⚠️ Likely causes:
Electrical issues (loose wiring or failing capacitor)
Faulty contactor relay
Debris near the outdoor unit
Why it matters: Buzzing could indicate a potential fire risk or a failing electrical component.
🛠️ What to do: This is best left to a certified HVAC technician—don’t try to fix electrical parts yourself.
3. Screeching or Squealing
🔊 What it sounds like: High-pitched, piercing screech ⚠️ Likely cause: A worn or misaligned blower motor belt, or dry motor bearings.
Why it matters: These parts can fail, leaving you without AC or heat when needed.
🛠️ What to do: Schedule a repair before the belt breaks or the motor seizes.
4. Rattling
🔊 What it sounds like: Loose change in a clothes dryer ⚠️ Likely causes:
Loose bolts or screws
A failing fan motor
Debris inside the unit or ductwork
Why it matters: A small loose part can become a big repair bill if it damages critical components.
🛠️ What to do: Check for visible debris if the sound is coming from your outdoor unit. Otherwise, call a technician to tighten and inspect components.
5. Whistling
🔊 What it sounds like: Wind blowing through a narrow gap ⚠️ Likely cause: Airflow restriction due to a clogged air filter, closed vent, or duct leak.
Why it matters: Reduces efficiency and increases strain on your system.
🛠️ What to do: Change your filter first. If that doesn’t help, inspect your ductwork for leaks or obstructions.
6. Popping or Cracking
🔊 What it sounds like: Sharp, brief pops—especially at startup ⚠️ Likely cause: Ductwork expanding or contracting due to temperature changes.
Why it matters: Usually harmless, but frequent or loud popping could indicate undersized or poorly insulated ducts.
🛠️ What to do: If ductwork becomes a nuisance, a ductwork inspection can help improve airflow and noise reduction.
7. Clicking
🔊 What it sounds like: Repetitive clicking during startup or shutdown ⚠️ Likely causes:
Relay issues
Faulty thermostat
Failing control board
Why it matters: Persistent clicking may prevent your system from starting properly and could indicate an electrical problem.
🛠️ What to do: Don’t wait—electrical issues can escalate quickly.
Hear Something Strange? Let’s Check It Out.
You don’t have to live with a noisy HVAC system. Whether you need a simple repair, a filter replacement, or a complete system evaluation, we’re just a call or click away.
At Thomas Hoffmann Air Conditioning & Heating, we pride ourselves on being a locally owned and operated HVAC company. With more than 30 years of experience and a master technician and mechanical engineer as our owner, we can replace, repair, and maintain your business or home’s HVAC system.
