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Why is My Air Conditioner Blowing Hot Air?

There are many reasons your air conditioner might be blowing hot air.

But before you call a technician, check the following to make sure the problem isn’t something you can fix without the help of a professional:
  1. Make sure your thermostat is set to “cool” instead of “heat”
  2. Make sure your fan is set to “auto” instead of “on”

Is your AC still blowing warm air after this? If so, you most likely need help from a professional.

Let’s take a look at 3 bigger issues that can cause this annoying problem.


Reason #1: Low refrigerant


Refrigerant absorbs heat from inside your home and dumps it outdoors. So if your AC is low on refrigerant, less heat is removed from the air, making it feel warm.

If you have low refrigerant, you may notice ice forming or a hissing noise (sound of refrigerant escaping) somewhere along the refrigerant lines.


What causes low refrigerant?


Your AC doesn’t use up refrigerant like a car uses up gas so the cause of low refrigerant is a leak. 


What should I do?


Call a professional to determine if you have a refrigerant leak. If you do, they should find and seal the leak before adding more refrigerant.


Reason #2: Dirty Evaporator Coils


The evaporator coil is filled with refrigerant that absorbs heat when air passes through them. This results in cool air that is pushed into your home.

But if the coils are covered in a thick layer of dirt, they can’t remove as much heat from the air, which is why the air from your AC feels warm instead of cool.


What causes dirty coils?


Evaporator coils get dirty when air filters are not regularly replaced or if your air filter isn’t catching enough airborne contaminants. This causes dust and dirt to build up on your evaporator coils.


What should I do?


Most of the time, your evaporator coils are located in the attic or basement so we don’t recommend trying to clean the coils yourself. Leave it to an AC technician who can also change your air filter, if needed.

We suggest keeping your evaporator coils clean with regular maintenance


Reason #3: Leaky Ducts


Your ducts are the connected tubes in your attic that deliver air throughout your home. If there is a leak in your ductwork, it can bring hot attic air (up to 130 degrees) into your home.

Duct leaks are not uncommon. In fact, in an average house up to 40% of air is lost via holes or poor connections in ductwork.

Because of their location, it can be hard to determine if cool air is escaping through your ducts. But some signs of duct leaks are:
  • High energy bills
  • Lots of dust in the air
  • Stuffy rooms or rooms that don’t cool off

What causes leaky ducts?


Wear and tear can result in holes or misalignment in your ductwork. Leaks in your ductwork can also be the the result of poor design and installation.

What should I do?


Get a professional to inspect your ductwork for necessary repairs.


Need help with an AC that’s blowing warm air?


There are many other reasons your AC may be blowing warm air, including issues with:
  • Wiring 
  • Electricity
  • The condenser (outdoor unit)

If you need help repairing your AC, contact Air Experts online and we’ll give you 10% off your scheduled appointment.

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