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Why Is My AC Blowing Hot Air? Common Causes and Solutions

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As St. Louis residents, we rely heavily on our air conditioning systems to keep us cool and comfortable during the sweltering summer months.

So when your AC starts blowing hot air instead of the refreshing coolness you expect, it can be frustrating and concerning. At Thomas Hoffmann Air Conditioning & Heating, we understand how disruptive this issue can be. Let’s explore why your AC might blow hot air and what you can do about it.

Why Is My AC Blowing Hot Air - Common Causes and Solutions
Very fast considering the weather we were having tonight. Really appreciate it for my mom. Thank you so much!
Response from the owner:Thank you, Felicia! We're glad we could help quickly, especially for your mom. Your appreciation means a lot to us!
Nick was on he way to our house when I had to cancel my appointment for service. Nick was very understanding and professional about it. While we didn't get to utilize him, I have no doubt he'd have been just as professional in his job.
Response from the owner:Thank you for your kind words. We appreciate your understanding and are glad to hear that Nick made a positive impression. If you ever need our services in the future, don't hesitate to reach out.
I couldn’t be happier with Thomas Hoffman. They are quick, courteous, and super knowledgeable as well as providing service at a good value. Most importantly to me, they have great integrity. I could not recommend them more highly!
Response from the owner:Thank you for your wonderful review, Josh and Nikki! We’re thrilled to hear that you had such a positive experience with our team. Providing quick, courteous, and knowledgeable service is our priority, and we're glad to know that our efforts resonate with our customers. Your recommendation means a lot to us!
Tom was a great service technician- arrived promptly on time - and fixed our issue within a few minutes!! Very nice guy too!
Response from the owner:Thank you for the wonderful feedback! We're glad to hear that Tom provided prompt and effective service. Our team strives to deliver a great experience, and it's fantastic to know that you were satisfied. If you need any assistance in the future, don't hesitate to reach out!
Very prompt and friendly service. Will definitely call them again.
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!
Tom Hoffmann has been servicing both our residential and commercial equipment for several years. Tom is an experienced, innovative engineer, he can troubleshoot and solve any problem that arises. He has even personally serviced our furnace on a holiday! The trust, communication, knowledge, and relationship we have built is why we choose Tom Hoffmann every time, and highly recommend him to all our colleagues
Response from the owner:Thank you, Dan, for your wonderful review and for highlighting Tom's dedication and expertise; we're grateful for your trust and support over the years!
This was my 1st time using Thomas Hoffmann A/C & Heating, but it will probably not be my last.
After calling 📞 a few companies near my location & not getting a response, I decided to call Thomas Hoffman & someone immediately answered.
I needed someone to comeout & look at the installation of a new Smart Thermostat & let me know if it was installed properly & if not, install it correctly for me.
I was given a appointment on the day that I called for later that morning with a gentleman named Nick who supposedly was the guy that knew all about Thermostats & Wiring.
Nick arrived & honestly saved the day. He was very personable & professional & did a very thorough job while explaining everything thoroughly.
Nick is a very valuable asset to the Hoffman company & represents their company & himself with great pride.
I felt like I was in safe hands, & Nick performed quality work.
Thomas Hoffman is a company that U can trust & get ur money's worth if not more.
I look forward to doing more business with them in the future....
Response from the owner:Thank you, Harlan, for sharing your experience with us! We're glad to hear that Nick provided such excellent service and made you feel confident in your Smart Thermostat installation. Your trust means a lot to us, and we look forward to serving you again in the future!
Giovanni hooked up and maintained my humidifier. He was very professional and polite. Thank you....
Sondra B.
Response from the owner:Thank you, Sondra, for your kind words about Giovanni's professionalism and politeness; we appreciate your feedback!
Good
Response from the owner:Thank you, Albert, for your positive feedback; we appreciate your support!
My family was having issues with our old water heater leaking gas so we called Thomas Hoffmann’s company to help us. Giovanni and Ryan changed our water heater and replaced it with a new one fast and efficiently. I would recommend anyone looking for efficient and reliable work to give them a call. Thank you guys again!
Response from the owner:Thank you, Michael, for your kind words! We're glad Giovanni and Ryan could assist you with your water heater replacement efficiently. Your recommendation means a lot to us!
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.
Giovanni and Ryan were great! Arrived on time, polite introductions, quality work and installed a new water heater in just a few hours. We have used them multiple times now and every time, they have been great!
Response from the owner:Thank you, Laura! We're so glad to hear that Giovanni and Ryan provided you with great service and quality work; we appreciate your continued trust in us!
Nick was a great technician to work with. He accurately assessed my problem and found a solution that will help keep my unit functioning without continued problems. Great and knowledgeable company.
Response from the owner:Thank you, Amond! We're glad to hear that Nick was able to provide you with a great solution and appreciate your kind words about our company.
Fast professional and curtious. I am so happy with the work and the energy
Response from the owner:Thank you, Richard! We're grateful for your kind words and glad to hear you appreciated the work and energy of our team.
Very quick to respond, and easy to work with. Replaced our furnace on a short timeline.
Response from the owner:Thank you, Brian, for your kind words! We're glad we could assist you quickly with your furnace replacement and make the process easy for you.
Super fast service and totally fixed the problem. Came out when no one self would.
Response from the owner:Thank you, Barbara, for your kind words and for recognizing our fast service; we're glad we could solve the problem when others couldn't.
Great service and price. Quick response
Response from the owner:Thank you, Bernard, for your kind words about our service and pricing; we appreciate your feedback and are glad you received a quick response!
The service man came out as requested. I called at night and he was here at 8:AM.
He figured out the problem and had it fixed within the hour.
Very courteous and efficient.
JGold
Response from the owner:Thank you, Joan, for your kind words. We're glad the technician was able to help you so quickly and efficiently. Your satisfaction means a lot to us!
Service was great
Response from the owner:Thank you, Chat! We're so glad to hear you enjoyed the service, and we appreciate your kind words.
Service was quick and professional, got our heat pump back up and working in a couple hours. Thank you!
Response from the owner:Thank you, Jake. We're glad to hear the service was quick and professional, and that your heat pump is up and running again!
Our furnace decided to stop working at 11pm on a Friday right before a bad winter storm. They took my call that night and had a tech (Duraid) out by 9am the next day and had us all fixed up within 15 minutes! Fantastic customer service. Thank you!!
Response from the owner:Thank you, Nicki! We appreciate your kind words and are glad Duraid could get your furnace up and running so quickly before the storm. Your satisfaction means a lot to us!
Thomas Hoffmann always does a great job in servicing our HVAC. Installed a new system last and it’s working great and very efficient. Nick goes above and beyond when servicing and answers all my questions. Highly recommend Thomas Hoffmann Air conditioning & Heating.
Response from the owner:Thank you, Nancy, for your kind words! We're glad to hear that you're satisfied with your new system and appreciate Nick's dedication to great service. Your recommendation means a lot to us!
They were professional and got my hot water back on. And I'm happy about that.
Response from the owner:Thank you, Pamela, for your kind words! We're glad our team was able to restore your hot water and meet your expectations.
Had a water pump leak and they were out the very next day to repair!
Response from the owner:Thank you, Andrew, for your kind words! We're glad we could quickly help with your water pump leak. Your satisfaction means a lot to us!
Great service and was very prompt. Service person was courteous
Response from the owner:Thank you, Mary, for your kind words about our service and the courtesy of our team; we appreciate your feedback!
Called at 5:50 on a Friday hoping to get an appt for next week. Guy on the line listened to my problem, diagnosed the problem over facetime, and gave me instructions as to how to change the filter on my unit with no problem at all. Fixed the problem and I didn't even have to pay a cent for it! I'll definitely be coming back here when we run into ore substantial maintenance problems.
Response from the owner:Thank you, James, for sharing your experience! We're glad our team member could assist you effectively and that you found the solution without any cost. We look forward to helping you with any future maintenance needs!
Awesome job! Nick was great. Prices are reasonable and well explained what I’m paying for and what work needs to be done.
Response from the owner:Thank you, Mitchell! We're glad to hear you had a great experience with Nick and that you found our pricing clear and reasonable. Your feedback means a lot to us!
Always professional, always on time and good value for the work that they do!
Response from the owner:Thank you, Jan, for your kind words about our professionalism and value; we truly appreciate your support!
As always, the Hoffmann technician 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!
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!
Nick Hoffman was amazing! He came out same day when our heat suddenly went out. He took the time to describe the problem and expertly fixed and tested it! Will definitely be recommending them. Thanks.
Response from the owner:Thank you, Matt! We're so glad to hear about your positive experience with Nick and that he was able to help you promptly. Your recommendation means a lot to us!
Job well done. The technician was competent and polite and knowledgeable. We'll have him back in the spring, honest company.
Response from the owner:Thank you, Laurel, for your kind words about our technician's competence and knowledge; we look forward to serving you again in the spring!
Realized my furnace stopped working late last night and forecast called for very cold arctic air blast. Called my regular HVAC company that advertises 24 hour service to find that after 7 PM, there is only an answering service. Same with two more “24 hour service” companies. Then I called Thomas Hoffmann HVAC Company and Nick quickly answered, listened to my issue, gave me a quote and was on his way. Nick arrived soon, completely checked out my furnace, found the problem and did the repair. Because the problem was fairly minor, he even gave me an unexpected and very appreciated discount. Nick was professional, competent, and very engaging. Best emergency, after-hours experience I’ve ever had. Nick saved the day and gave me the peace of mind I needed.
Response from the owner:Thank you, Richard, for sharing your experience; we're glad Nick could provide you with prompt and professional service during such a challenging time. Your kind words mean a lot to us!
Nick was great he was prompt and very patient in explaining the problems with our system and the steps we would take to solve them.

I highly recommend using Thomas Hoffman Air Conditioning and Heating!
Response from the owner:Thank you, Benjamin, for your wonderful feedback about Nick's promptness and patience; we appreciate your recommendation of Thomas Hoffman Air Conditioning and Heating!
Nick was friendly, professional and knowledgeable, he did an awesome job!!
Response from the owner:Thank you for recognizing Nick's friendliness, professionalism, and knowledge - we're glad you had an awesome experience!
Great customer service! Very knowledgeable
Response from the owner:Thank you, Rob! We're glad you had a great experience and appreciate your kind words about our knowledgeable team.
Furnace would not blow heat on Friday night and after leaving a few messages to several companies, Mr Hoffman called me back quickly and did a service call. Diagnosed the issue and was able to fix the problem. Will need a new unit soon, but nice not be without heat during the holidays! Quote and Invoice receipt done on the spot and detailed! Will use again for sure.
Response from the owner:Thank you, Heath, for your kind words! We're glad Mr. Hoffmann could get your furnace working in time for the holidays and provide a detailed quote and invoice. We appreciate your trust in us and look forward to helping you again in the future!
Fast, friendly and very cooperative.
Response from the owner:Thank you, John, for your kind words; we're glad you had a great experience with our team!
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Top Reasons Your AC May Be Blowing Hot Air:

  • Thermostat Issues
  • Dirty Air Filter
  • Low Refrigerant Levels
  • Frozen Evaporator Coil
  • Compressor Problems
  • Outdoor Unit Issues
  • Leaky or Damaged Ductwork
  • Incorrectly Sized AC Unit

Let’s dive deeper into each of these issues:

Thermostat Issues

Before diving into more complex problems, always start with the simplest explanation. Check your thermostat to ensure it’s set to “cool” mode, and the temperature is lower than the current room temperature. Sometimes, the issue is as simple as an accidental switch to “heat” mode or a thermostat that needs new batteries.

Dirty Air Filter

A clogged air filter is one of the most common culprits behind an AC blowing hot air. When your filter is dirty, it restricts airflow, causing your system to work harder and potentially overheat. This can lead to warm air coming from your vents. We recommend checking and changing your air filter every 1-3 months, depending on usage and household factors like pets or allergies.

Low Refrigerant Levels

Refrigerant is the lifeblood of your AC system, responsible for absorbing heat from your home’s air. If your system is low on refrigerant, often due to a leak, it can’t effectively cool the air. This results in warm air blowing from your vents. If you suspect a refrigerant issue, contacting a professional HVAC technician is crucial, as handling refrigerant requires specialized training and equipment.

Signs of Low Refrigerant:

  • Warm air from vents
  • Hissing or bubbling sounds from the AC unit
  • Ice formation on refrigerant lines or evaporator coil
  • Higher than average energy bills

Frozen Evaporator Coil

Ironically, a frozen evaporator coil can cause your AC to blow hot air. This can happen due to restricted airflow (often from a dirty filter) or low refrigerant levels. When the coil freezes, it can’t effectively absorb heat from your home’s air. If you notice ice on your outdoor unit or indoor air handler, turn off your system and call for professional service.

Compressor Problems

The compressor is the heart of your AC system and is responsible for pressurizing and circulating the refrigerant. If it’s not working correctly, your system won’t be able to cool the air. Compressor issues can range from electrical problems to mechanical failures and typically require professional diagnosis and repair.

Outdoor Unit Issues

Your AC system consists of both indoor and outdoor components. If the outdoor unit is dirty, blocked by debris, or not receiving power, it can’t effectively release the heat absorbed from your home. This results in the system recirculating warm air. Ensure your outdoor unit has clear space around it and is free from leaves, grass clippings, and other debris.

Leaky or Damaged Ductwork

Sometimes, the problem isn’t with your AC unit but the ductwork that distributes the air. Leaks or damage in your ducts can allow hot attic air to mix with the cooled air, resulting in warm air from your vents. Professional duct inspection and sealing may be necessary to resolve this issue.

Incorrectly Sized AC Unit

If your AC system is too small for your home, it may struggle to cool the air effectively, especially on the hottest days. Conversely, an oversized unit might cool your home too quickly, leading to short cycling and poor humidity control. Both scenarios can result in inconsistent cooling and potentially warm air from your vents.

At Thomas Hoffmann Air Conditioning & Heating, we have the expertise to diagnose and resolve various AC issues. Our team of certified technicians can quickly identify the root cause of your AC blowing hot air and provide practical solutions to get your system back to peak performance.

Remember, regular maintenance is vital to preventing many of these issues. Schedule annual tune-ups with our team to keep your AC system running efficiently and extend its lifespan.

Don’t suffer through the St. Louis heat with a malfunctioning AC. If your system is blowing hot air or experiencing other cooling issues, contact Thomas Hoffmann Air Conditioning & Heating today. We’re here to ensure your home stays relaxed and comfortable all summer.

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