Why Is My Air Conditioner Blowing Hot Air? A Florida Tech Explains

April 15, 2020

Why is my ac blowing hot air

Feel warm or even hot air coming from the vents of your AC? That’s a problem.

We wish we could tell you there was one, simple answer as to why your AC is blowing warm air, but the truth is, hot air coming from your AC could be caused by a variety of different reasons. 

A few of the most common reasons your AC is blowing warm air include: 

  • Wrong thermostat setting

  • Dirty outdoor (condenser) unit

  • Dirty evaporator coil

  • Tripped circuit 

Throughout this blog, we will go into more detail about each of these issues, to hopefully help you determine why your AC is blowing hot air and what you can do to fix it. 

If you’d rather have a professional come and take a look at your AC system, you can learn more about our ac repair service or contact us to schedule an appointment

Potential Cause #1: Wrong thermostat setting

You should ensure that your thermostat is set to:

  1. COOL instead of HEAT

  2. AUTO instead of ON (ON allows your system’s fan to blow air even when that air has not been cooled by your AC, whereas AUTO only turns the fan on when there is cool air to blow).

Thermostat set to AUTO instead of ON

The settings your thermostat should be on if you want to cool your home.

If you’ve checked your thermostat settings and they are correct, but your AC is still blowing hot air, keep reading. 

Potential Cause #2: Dirty outside (condenser) unit

example of a dirty condenser on an outdoor unit

An example of a dirty compressor (outdoor unit).

Your AC cools your home by absorbing heat from your home’s air and transferring it to your outside unit where it’s released. 

However, if your outdoor AC unit is caked in dirt or visibly clogged by tall grass or bushes, your system won’t be able to release as much heat as it needs to, and your AC will struggle to cool your home’s air.

Solution: Get your AC coils cleaned. You can clean them yourself with a coil cleaner or have a tech clean them for you as part of a preventative maintenance plan.

If you want to prevent your outdoor AC unit from getting clogged with grass, sticks and leaves, you should clear a 3-foot radius around it.

Example of foliage that is growing too close to your AC system

An example of foliage that is growing too close to your AC system.

Potential Cause #3: Low refrigerant

Example of Refrigerant Line

Refrigerant is a liquid/gas substance that transfers heat from inside your home, outside. If your AC is low on refrigerant, your system can’t absorb much heat from your home’s air. This means your AC won’t be able to produce enough cool air, which can lead to your AC blowing warm air back into your home.

Solution: Contact an HVAC technician. Refrigerant doesn’t get used up over time, so if your AC system is low on refrigerant, it means you have a leak. To fix this, a professional will need to find the leak, drain out the remaining refrigerant, repair it, and then add the right amount of refrigerant back into your system. 

Note: Refrigerant is a toxic substance, so this is not a repair you should attempt to fix on your own. 

Potential Cause #4: Dirty evaporator coil

The inside of an evaporator coil.

The inside of an evaporator coil.

Your evaporator coil is the part of your AC where heat is transferred from your home’s air to your refrigerant lines. The evaporator coil is full of refrigerant, and when warm air from your home is blown over those coils, the heat is absorbed by the refrigerant. 

However, if your evaporator coil is clogged with dirt, it will block the heat transfer from the air to the refrigerant, meaning the heat from your home won’t be absorbed and unconditioned (warm) air will be recycled back into your home.

Solution: A dirty evaporator coil is usually caused by a dirty air filter or by running your AC without a filter. If your evaporator coil is dirty, you’ll need a professional to properly clean it. However, if you want to prevent your coil from becoming dirty in the future, you should check your air filter and replace it if it’s dirty about once a month. 

Note: If you don’t want to go to the store to purchase an air filter, you can shop at our online store here

A clean air filter (left) vs. a dirty air filter (right)

A clean air filter (left) vs. a dirty air filter (right). If your filter looks like the filter on the right, its time to replace it.

Potential Cause #5: Tripped circuit

Tripped Circuit Breaker

Most AC’s have two breakers: one for the outside unit and another for the inside unit. If the outside unit’s breaker is tripped, then the inside unit will continue to blow air into your home–the air just won't be cooled.

Solution: Check your breaker box and see if the outdoor unit’s breaker is tripped (the electrical panel should be labeled HVAC or AC). If so, switch it back on by:

1. Turning the breaker OFF (to the right) 

2. Turning the breaker ON (to the left). Wait 30 seconds for the breaker to reset.

If it trips again, contact a professional ASAP to help you. A blown fuse or a circuit that continually trips indicates deep-seated wiring problems. Do NOT reset the breaker again. Multiple overcurrents can lead to major AC damage and serious electrical issues that could cause a fire.

Need a professional to take a look? Contact the best HVAC team in Florida: Advanced Air

If you’ve tried all of the above (or have an issue that you’ll need a tech to fix), you can reach out to us for help. 

We serve many parts of Southwest Florida—including Fort Myers, Naples, Cape Coral, Bonita Springs, Estero, Port Charlotte and more. 

Give us a call or contact us online and we can help get your AC system blowing cool air into your home again.