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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
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.
Nick did an amazing job, on time, very knowledge and professional.
Response from the owner:Thank you for the great review, Joe. We look forward to servicing you in the future!
installed humidifier and hepa filter. Very pleased with service.
Response from the owner:We are happy to hear that you had a pleasant experience!
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.
I would describe the overall experience as professional, but also kind and responsive from the initial phone call to the technician.
Response from the owner:Thank you for your kind review! We appreciate your business and look forward to helping 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!
Nick was amazing. He came out the same day and had our heater fixed quickly
Response from the owner:We are so happy to hear you had a pleasant experience with us!
Hoffman plumbing came out to help with some of my plumbing problems. They were amazing. I wish I would have called them first
Nick did a great job!
Response from the owner:We're happy 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!
woke up to a very cold house, called Thomas Hoffmann, they were able to come out a couple of hours later and get the issue resolved. Always trust them, they have always been quick to respond and get either the heating or ac issue fixed that day. Also a great price!!!! give them 10 stars if i could, Thank You JS
Response from the owner:Thank you for the kind review, Jim. We are happy to hear that you had a positive experience working with Thomas Hoffmann!
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!
From the phone to the completion of the job everyone is so polite and informative.
Response from the owner:Thank you for the kind review, Frank! We appreciate you and your business.
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 .
Response from the owner:We are so happy to hear you had a great experience, Sam! Thank you for the review, and thank you for your business.
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!
Notified me of expected arrival time and then again when he was on his way and was exactly on time! Nick was very personable and trustworthy.
Response from the owner:Thank you, Maureen. We're glad to hear that Nick kept you informed and made your experience enjoyable!
Very fast service, Nice young man, and personable!
Response from the owner:Thanks for the great review, Christina! We appreciate your kind words and your business.
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.
Jeff did an outstanding job. Assessed the situation, found the problem, and fixed it within the hour. Thank you!
Response from the owner:Thank you, Jaden! We're glad to hear that we provided such prompt and effective service. Your appreciation means a lot to us!
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!
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!
Came out immediately after a time slot opened and fixed the AC issue.
Response from the owner:Thank you, James, for your kind words! We're glad we could address your AC issue promptly.
Speedy response and service. Knowledgeable professional. Kind, courteous, friendly but professional.
Response from the owner:Thanks for the great review! We appreciate your business and look forward to working with you in the future.
Super Helpful and Honest Service

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.
Excellent experience.
Response from the owner:Thank you, Laura, for your 5-star review! We appreciate your support.
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!
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.

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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