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.
Love that it’s the same technician every time. Let’s me know what he found and any concerns he might have regarding our units. Great customer service.
Response from the owner:Thank you, Theresa! We're glad to hear you appreciate having the same technician and the communication about your units. Your feedback on our customer service means a lot to us!
From the phone to the completion of the job everyone is so polite and informative. I had Giovani as our representative and he was very informative and professional, and knew exactly what the problem was. Thanks so much.
Response from the owner:Thank you for the kind review, Frank! We appreciate you and your business.
Zach did an excellent job! Always courteous and friendly. We would highly recommend calling Thomas Hoffmann HVAC for any heating and cooling needs.
Response from the owner:Thank you, Allan! We're glad to hear that Zach provided excellent service and appreciate your recommendation for Thomas Hoffmann HVAC.
Was able to locate the problem right away and replace a switch and add Freon very nice job by this employee. I will recommend Thomas Hoffman for future references.
Response from the owner:Thank you, William! We're glad to hear that our team was able to quickly address the issue and that you had a positive experience with Thomas. Your recommendation means a lot to us!
I had Nick come out. He was awesome. Very knowledgeable, prompt and helpful. I will definitely recommend Thomas Hoffmann HVAC to others in need of HVAC support.
Response from the owner:Thank you, Jack! We're glad to hear that Nick provided you with excellent service. We appreciate your recommendation and look forward to assisting you and others in the future.
From our initial quote until the new furnace and AC were completed, everything was smooth and efficient. Zachary and Giovanni were excellent on-site, taking time to explain the installation as well as leaving the home clean. Thank you Thomas Hoffmann team
Response from the owner:Thank you! We're glad to hear that the installation process was smooth and efficient. Zachary and Giovanni will be pleased to know their efforts made a positive impact. We appreciate your kind words about the team!
Update 4/6/26: Zach Sperling is such a pleasant and knowledgeable technician that I recommend him highly. Thomas Heating has been a wonderful company to work with in my maintenance plan. If you are looking for a reputable company, look no more.
This company is so responsive that I love them. They respond immediately, and I trust them to tell me what needs to be done. I haven’t been steered wrong yet. They are genuinely nice to work with and honest. I use their maintenance program which I highly recommend.
Response from the owner:Thank you for your kind words, we truly appreciate your trust in us and are glad to hear about your positive experience with our services.
work good but got at least 6 messages from them very annoying
Response from the owner:Thank you for your feedback, Harold. We appreciate your input and understand how too many messages can be frustrating. We'll work on improving that experience for you.
Nick was great! He came right out and was able to solve the problem fairly easily. He communicated well and helped us prevent a future problem as well.
Response from the owner:Thank you for the review, Philip! We are happy to hear you had a pleasant experience working with us.
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.
They have never failed to fix my hvac problems. These folks are top tier.
Response from the owner:Thank you for the wonderful feedback, Greg! We're glad to hear that you've had such positive experiences with our team. Providing timely and effective service is our priority, and we're here whenever you need us. Looking forward to assisting you again!
Giovanni was very professional, helpful, patient and helped me figure out the issue, if it was covered under warranty, and next steps. Great overall experience and much appreciated.
Response from the owner:Thank you, Amy! We're glad to hear that Giovanni provided you with such professional and helpful service. Your appreciation means a lot to us!
Always professional and thorough whenever they service our home. We have used Thomas Hoffmann Air Conditioning & Heating multiple times since we moved into our home and will continue to use them in the future.
Response from the owner:Thank you for the thoughtful review, Joe. We appreciate you and your business!
0 stars if I could. Bought a faulty (not to mention overpriced) surface igniter, called back five minutes later after installing, of course they didn’t stand behind their part. Go to Grainger instead. Same (working) part, half the price.
Response from the owner:Hi there. I am unable to locate your customer profile. Please give our office a call at 314-471-7625 so we can get this figured out for you.
My furnace was not working. A very nice gentleman came out this morning and fixed the problem and now I have much needed heat. He was very professional and courteous. I will definitely be using them again when the need arises.
Response from the owner:Thank you for the positive feedback! We're glad to hear that you were pleased with our prompt and friendly service. We look forward to assisting you again in the future!
I will always call Hoffmans for my air and heat needs. They were out to my daughters house that day and fixed it. It was right before the weekend storm with below zero temps the next day. They saved my daughter and grandbabies. I could never thank them more.
Response from the owner:We are so happy to hear that we could help! Thank you for the kind review.
Snow and drifting snow covered intake and out take vents causing the furnace emergency to shut off furnace. Cleaned off the driftibg/ snow off roof and vents furnace works perfect now. Thank you and great job Nick.
Response from the owner:Thanks for the great review, Scott! We appreciate your support.
5 stars! Nick was here to fix my heater within 2 hours of my call. He explained the problem to me thoroughly and got the job done quickly & professionally. Thank you so much!
Response from the owner:Thank you for the kind review, Jennifer! Glad we could help.
Extremely thorough and educational. They do a wonderful job of explaining everything and making sure I was comfortable knowing how the systems worked in my house!
Response from the owner:Thanks for the great review, Matthew! We appreciate your support.
I noticed a strange noise that I was concerned was linked to my furnace. I called Thomas Hoffman Heating & Cooling and Nick came right out. He was very thorough checking all components. Thankfully all checked out for us this visit. Definitely recommend Thomas Hoffman Heating & Cooling!
Response from the owner:Thank you so much for the kind review, Abby! We appreciate your business and look forward to servicing you in the future.
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!
Got a quote over the phone. Everything was explained thoroughly. Dakota, my technician arrived and on time, was very professional and knowledgeable. He didn’t try to upsell or change anything. He did a great job. We can already tell the difference since the ducts and vents were cleaned. Would recommend an use Hoffman again in the future.
Response from the owner:Happy to hear you had a pleasant experience using Thomas Hoffmann!
The technician, Ryan, was knowledgeable and helpful in identifying the issue with our mini split AC unit. They are the second company we called after issues with the first and will be using Hoffmann again.
Response from the owner:We are so happy to hear your experience with Thomas Hoffmann was pleasant. Thank you for your kind review, & we look forward to working with you in the future!
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.
