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.
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!
Zach was very professional and thorough. He was nice and did a great job!
Response from the owner:We are happy to hear you had a great experience with our company. Thank you for your kind words, Mike!
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!
Polite and very efficient.
Response from the owner:Thank you for the 4-star rating, Debra!
Fast, friendly, professional service.
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!
Great service and arrived on time when promised.
Response from the owner:Thank you Wray, for your kind words! We're glad to hear you had a great experience and that everything was on time.
Ryan was knowledgeable and figured out why our furnace wasn’t working and repaired the problem
Response from the owner:So happy to hear you had a good experience with the team here at Thomas Hoffmann, Jo! Thank you for your support.
Service was great on time very efficient explained what he was doing changed filter disposed of old filter ! Nice young man 👍
Response from the owner:Thank you, marianne, for your fantastic 5-star rating; we appreciate your support!
Wonderful work. Great communication and always a happy positive technician. Answered all of my questions with sincerity and patience.
Response from the owner:Thank you for the kind words, Bob. We truly appreciate your business!
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!
Hoffman is great! Very professional and thorough.
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.
Giovanni was great today! Thanks for everything.
Response from the owner:Thank you, James! We're glad you had a great experience, and we'll be sure to pass along your kind words to Giovanni.
The technician is always on time and very thorough.
Response from the owner:Thank you, Catherine, for your kind words about our technician's punctuality and thoroughness; we appreciate your feedback!
Giovanni was good…. This is reason we ask for him
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.
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.
Ryan was here on time. Thanks for getting here early, as I requested. Very friendly too. It was my annual checkup and all good!
Response from the owner:Thank you so much for the great review, Kay. We truly appreciate your business!
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!
Same day service. Technician arrived as scheduled. Replaced capacitor quickly. Friendly technician. Repair cost $429 seemed high for inexpensive part and 20 minutes labor.
Response from the owner:Thank you, Tom, for your feedback! We're glad to hear the technician was prompt and friendly, though we understand your concerns about the repair cost. We appreciate your insights and hope to serve you again in the future.
Excellent.
Response from the owner:Thank you so much, Al, for your excellent review; we truly appreciate your support and are glad to hear you had a great experience!
Thank u
Response from the owner:Thank you, Connie, we appreciate your feedback and are glad to hear from you!
Courteous friendly and efficient! What else could you want!
Response from the owner:Thank you, Bob! We're glad you found our service courteous, friendly, and efficient – that's exactly what we strive for!
Thomas Hoffmann is the most professional and courteous of all the HVAC companies in St. Louis. It has kept my HVAC systems in good working order through the hottest and coldest days for many years.
Response from the owner:Thank you, Jonathan, for your kind words about our professionalism and courtesy; we truly appreciate your support!
Quick response time and great to deal with!
Response from the owner:Thank you, Pat! We appreciate your kind words and are glad to hear you had a positive experience with our team.
I notified two companies at the same time regarding a malfunctioning AC unit and Wow! Super fast response from Hoffmann on a weekend no less, to fix our AC unit. Hoffmann’s tech responded to my call immediately and fixed our AC before Galmiche has even responded. Used to be a Galmiche customer, but will use Thomas Hoffmann from here on out!
Response from the owner:Thank you, Darlene, for your fantastic feedback! We're glad to hear that our team was able to respond quickly and resolve your AC issue. We appreciate your trust in us moving forward!
Ryan did a great job with my AC reinstall. Very knowledgeable company with Tom Hoffmann providing the engineering expertise.
Response from the owner:Thank you, Steve! We're glad to hear that Ryan did a great job on your AC reinstall, and we appreciate the shoutout to Tom's expertise. Your satisfaction means a lot to us!
These guy's are amazing same day service very well priced for the knowledge they have ask before doing anything to confirm they're my new go to
Response from the owner:Thank you, Cory! We're glad you found our service amazing and appreciate your kind words about our pricing and knowledge. We're here for you anytime!
They came very fast to fix our AC and service was very good
Response from the owner:Thank you, Maria, for your kind words about our service; we're glad to hear you had a great experience!
My ac compressor was replaced. They always do a good job and they are always available when you need them.I think the price was a little too high since they only had to change the compressor in my unit. The compressor was under the warranty. Other than that Im very satisfied with the job the technician did.
Response from the owner:Thank you, Carlos, for your feedback and for recognizing the hard work of our technician; we appreciate your satisfaction with the job done and will take your pricing comments into consideration.
I was very pleased with your service. Prompt response would was most appreciated. The technician was very knowledgeable and prepared for the work. Also he was very personable and professional.
Response from the owner:Thank you, Richard, for your kind words; we appreciate your recognition of our technician's knowledge and professionalism, and we're glad you had a positive experience with our service.
Nick zeroed right in on the problem with a slight leak and quickly provided a solution.
Response from the owner:Thanks, George, for your kind words! We're glad Nick could quickly address the issue for you.
I have complete trust in Thomas Hoffman AC . I have had multiple
technicians who are always polite and knowledgeable.
Response from the owner:Thank you for your trust in our team, Henry! We appreciate your kind words about our technicians.
Speedy and knowledgeable service!
Response from the owner:Thank you, Zach, for your kind words; we appreciate your support!
Thank goodness for them coming out so quickly. Got our whole job done and we are COOL again. Thanks so much!!!
Response from the owner:Thank you, Sandy! We're so glad to hear everything got done quickly and you’re feeling cool again. We appreciate your kind words!
Had an amazing experience with Thomas Hoffman. They were very professional and solved the problem quickly. I would highly recommend!
Response from the owner:Thank you, Alex, for your wonderful feedback! We're glad to hear that Thomas was able to assist you so effectively. Your recommendation means a lot to us!
Nick was a true expert in explaining our options for a new thermostat.
Response from the owner:Thank you, Robert, for your kind words about Nick's expertise; we're glad he could help you with your thermostat options!
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.
👉 Schedule your HVAC noise inspection today with Thomas Hoffmann Air Conditioning & Heating.
24/7 Service Call Now
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.
