You turn on the air conditioner one summer afternoon, sit down to await the cool air, and instead you feel warm air blowing out of your vents. There are a few different reasons why your central air conditioner can start blowing warm air. Some of the reasons have easy checks and fixes while others will require a visit from an air conditioning repair person.
Here are a few of the reasons why your central air conditioner could be blowing warm air inside – and how to fix the problem.
The thermostat is the first place you should start whenever you seem to have temperature issues. Make sure the settings are in the right places and that someone hasn't bumped on the heat or turned the unit onto fan-only mode. You should also change the thermostat's batteries if you haven't done so in a while, as dying batteries can make the thermostat send the air conditioner faulty signals.
If you finish all of the other checks elsewhere in the unit and nothing seems wrong, you should have an HVAC tech make sure you aren't having an electrical issue in your thermostat. Replacing the thermostat should fix the problem.
Dirty or Frozen Evaporator Coils
Evaporator coils are located in the air handler inside your furnace. The coils receive liquid refrigerant from the condensing unit outside your home and convert that liquid to a gas. The phase change causes the coils to become very cold. A blower fan cycles warm air out of your rooms, across the coils, then pushes that cold air back out into your rooms.
Dirty or frozen over coils can prevent this process from working properly. Frozen coils might sound like they should make colder air but, as with dirty coils, the obstruction means that the coils are less efficient at converting refrigerant on its next cycles through and eventually stops cooling any more.
You can check the coils yourself by turning off all of the electricity to your furnace and then removing the back cover. The coils should be easy to spot near the bottom of the unit. Check to see if the surface of the coils looks dirty or icy then clean the coils with a foaming cleanser that doesn't require rinsing. After the cleanser has been left for the time indicated on the package, put the furnace back together, restore the power, and test to see if the air is now blowing cold.
Evaporator coils that continuously freeze or warm air with no other identifiable cause can both indicate a problem with the refrigerant or fuel that runs your cooling system. Only licensed HVAC technicians, such as those at Arlington Heating & Air Conditioning, are allowed to purchase and work with the hazardous refrigerant, so you want to leave this task up the professionals.
The tech might need to add more refrigerant to the system or change the refrigerant if a previous tech filled it with the wrong kind of refrigerant.