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Why Is My AC Blowing Hot Air? A San Marcos Tech Answers

October 06, 2022

Is your air conditioner blowing hot air?

Amidst high heat and humidity in the San Marcos, TX area, a poorly functioning air conditioner is a serious problem. You probably wonder about the underlying problem if you feel warm air coming from your air vents. Understandably, you want to restore your home’s comfort ASAP.

So, what’s causing your central AC to blow warm air? The most common reasons include:

  • Your thermostat is set to the wrong mode
  • Your air filter is dirty
  • Your outdoor unit has issues
  • You have a refrigerant leak
  • You have leaky or disconnected ductwork

In this blog, we’ll go into detail about each of the above problems to help you diagnose your AC’s issue and how you can fix it yourself or with professional assistance.


Want an HVAC Professional to Diagnose Your AC ASAP?

If you’d rather a professional take a look at your AC, diagnose it, and repair it immediately, contact Reliable Air. Our technicians undergo rigorous and regular training so you can be confident that they will do your AC repair job right the first time. Call us at (512) 396-8183 or schedule service online today!


Your Thermostat Is Set to the Wrong Mode

Make sure your thermostat is set to AUTO

It sounds minor, but ensuring your thermostat is set to “COOL” mode and “AUTO” can save you an unnecessary AC repair.

A household member may have accidentally switched your system to “HEAT” and “ON” modes instead of “COOL” and “AUTO.” Some thermostat models also make it easy to toggle the switch too far. If this is the cause, you’re in luck because you can easily switch them to the right settings.

Why is it important for your thermostat to be on these settings? If it’s set to “ON,” the air conditioner’s fan will continuously run, regardless of whether it’s actually on a cooling cycle (thereby blowing warm or room temperature air). In contrast, a thermostat set to “AUTO” ensures that the fan only turns on when there’s cold air to push out.

Your Air Filter Is Dirty

Change out your air filter whenever it’s dirty.

Another easy way to troubleshoot your air conditioner blowing warm air? Look at the state of your air filter. A dirty one clogged with dirt and debris particles can block airflow coming into the system.

Why is that a problem?

Air conditioners have a part called the evaporator coil that houses refrigerant, which is the cold chemical agent that actually removes heat from the indoor air. This air conditioner part is frigidly cold. However, the warm air your AC takes in counterbalances the cold. With a dirty air filter, not enough warm air enters the system and freezes the evaporator coil. So, a frozen evaporator coil will restrict your AC’s ability to cool your home, which is why you feel warm air circulating instead of cold.

Check your air filter to see if it’s clogged with dirt. Replace it with a new one and let your AC run for a bit to see if the air blowing out feels colder. If not, contact a professional HVAC technician for an AC inspection, diagnosis, and repair. You can also enroll in an HVAC maintenance plan, and a technician will come out to replace your air filter, clean your AC, and perform any necessary inspections and repairs before the next cooling season starts.

Check Your Outdoor Unit

Make sure your outdoor AC unit has power and the compressor is working.

Check That the Outdoor Unit Has Power

If the outdoor unit is not receiving electrical power, the inside compressor won’t function. AC compressors are the metaphorical heart that pumps and circulates refrigerant (the “blood”) throughout your system. As we touched on above, it’s the chemical agent that actually removes heat from your home’s air. If the compressor doesn’t work, your air conditioner won’t be able to push out cold air.

An outdoor unit without power is usually due to:

  • A tripped circuit breaker: Air conditioners use the most amount of energy to start up. This is why we recommend homeowners turn down their AC instead of shutting them off entirely. If they draw too much energy, they can trip your circuit breaker. Check your electrical panel and find the AC circuit breaker. If it’s tripped, make sure to reset it. However, do not reset it again if it trips again.
  • A broken thermostat relay switch: A broken wire in your thermostat won’t be able to communicate with your AC system to turn on and cool. As a consequence, the power connection to your outdoor unit gets cut.

Check That the Compressor Has No Issues

If your air conditioner has power, it could be that the compressor itself broke.

As your AC ages, the compressor may start to fail. When it malfunctions, your system won’t cool your home as it used to, causing warm air to blow from your air vents.

Your compressor may have issues if you notice the following signs:

  • Loud noises coming from your outdoor AC unit
  • Weak airflow coming out of your vents
  • AC circuit breaker keeps tripping

Hire an HVAC professional to determine whether your compressor is the cause of the hot air. Since the compressor is typically an expensive part to replace, they might recommend replacing the entire system over replacing just one part.

Low Refrigerant Levels

As we’ve mentioned above, refrigerant is the substance that actually cools your home’s air. So, it makes sense that if there isn’t enough refrigerant in your air conditioner, the air coming out of your vents won’t be very cold.

Note: Low refrigerant levels mean that you have a leak somewhere. Air conditioners do not just “run out” of refrigerant because it only runs in a closed loop in your system. You will need to call a certified professional to find the leak, repair it, and recharge the refrigerant, as the substance is toxic.

Signs of a refrigerant leak include:

  • Hissing/bubbling noises near the outdoor unit
  • Increased energy bills
  • Water pooling around the indoor unit
  • Ice on the refrigerant lines

Leaky or Disconnected Air Ducts

Ductwork in attic

Check that your home’s ductwork has no leaks.

Leaks in your home’s ductwork allow warm air from areas like your crawlspaces or attics to mix with cooled air, making the air coming out of your vents warmer. Other signs you have leaky or disconnected ducts include:

  • Dusty air vents
  • Higher-than-normal energy bills
  • Uneven cooling throughout your home

According to EnergyStar, duct sealing can improve a home’s energy efficiency by up to 20%. An improvement in energy efficiency also reduces your monthly energy bills and makes your home colder in Texas’ humidity. Contact an HVAC professional to inspect your ductwork and fix any leaks you may have.

Need a Trusted San Marcos Technician to Fix Your AC Issue? Call Reliable Air!

AC Installation in San Marcos, TX

Contact Reliable Air for a trustworthy AC repair in San Marcos.

We offer same-day AC repair services for homeowners in San Marcos, TX and the surrounding areas. You can trust that we only hire professional and courteous technicians who can fix whatever is causing your warm air issues so that your AC can properly cool your home again.

With a reputation for honest pricing, reliable workmanship, and technicians who always clean up after themselves, we’ve earned the loyalty of Texas homeowners for nearly 30 years.

Call us at (512) 396-8183 or schedule service online today!