Hot Air: Why Is My AC Blowing Hot Air?

There are some simple checks that you can carry out to determine the potential cause of the hot air. We have listed 5 of the most common causes below, starting with the simplest, to the more complicated, requiring the expertise of licensed technicians:

• Wrong Thermostat Setting: If you are lucky, this will be the simplest fix that you will never forget: double-check that your thermostat is set to ‘heat’ instead of ‘cool’, and that the fan is set to ‘auto’ instead of ‘on’. The latter setting runs the fan all the time, even when the AC unit is not on a cooling cycle.
• Loss of Electricity: This is another easy check to conduct on split systems: if the outdoor unit has lost power, the indoor unit will be blowing warm air from your home’s vents. You can check your circuit breaker and the emergency switch on the outdoor AC unit to verify it is set to ‘on’. If your AC circuit breaker repeatedly trips, you should contact a technician or an electrician to verify that your breaker can handle your AC’s current draw.
• Dirt in Your Unit: Your AC needs a clean path to deliver cool air. Dirt or debris anywhere in the system will restrict the movement of cool air. For split systems, you should keep the area around your outdoor unit clean and clear. You should also check that the air filters are clean. Dirty air filters can be replaced or cleaned, depending on which type your AC uses.
• Frozen Evaporator Coil: We are now entering more technical territory: Air conditioners need good airflow to wick off the condensation that has cooled on its evaporator coil. When the airflow across the evaporator coil is reduced, the coil’s temperature drops, causing it to freeze. A frozen evaporator coil cannot absorb heat out of the air, and your AC will blow warm air. There are several causes for this, from low refrigerant levels to mechanical issues. The investigation may involve shutting off power to your AC unit to check the coils for frost or ice. This is best done by a licensed technician.
• Refrigerant Leaks: Refrigerant is the substance that carries heat out of your home. Leaking refrigerant means that the air conditioner does not have enough ‘charge’ to carry the heat out. So, the air being blown into your house will be warm. Refrigerants can be dangerous to handle. You should contact a licensed technician if you suspect a refrigerant leak.