Is your air conditioner's inside unit covered in ice? Is frost building up on the refrigerant lines? Are you getting very little air from your vents?
There are a variety of things that could cause this, but we’ll cover the 2 biggest ones.
But first, turn off your air conditioning system. Running your air conditioner with it like this could harm the compressor (an important and expensive part).
Then, turn your thermostat’s fan setting to “on” to thaw the ice in the inside unit.
OK, now that we’ve gotten that out of the way, here are 2 reasons this is happening.
Airflow issues
By “airflow” we mean the air flowing over the evaporator coil (the tubes that have cold liquid refrigerant running through them).
Normally, the inside AC unit pulls in your indoor air and blows it over the evaporator coil. This allows your refrigerant to absorb the heat so your air is now nice and cool.
But if anything stops, blocks or restricts air from flowing over the coil, it gets too cold. So any condensation/moisture that builds up on the coil quickly ices up.
Common causes of airflow issues include:
Dirty air filter (change the filter once a month during summer)
Closed supply vents
Return grills covered by drapes, curtains or furniture
Dirt on the evaporator coil (the dirt insulates the coil from warm air)
Improperly sized ductwork
Bad blower motor (the blower needs to pull in enough air over the evaporator coil)
Low refrigerant and refrigerant leak
When your air conditioner is low on refrigerant, pressure drops in the system and the temperature drops along with it. The evaporator coil gets too cold and freezes up. It’s just like when you spray a compressed air duster and the can gets super cold.
Where there’s low refrigerant, there’s usually a refrigerant leak because refrigerant isn’t used up like gas in a car.
Have a professional look for the leak and get an estimate for repair before refilling your air conditioner with refrigerant. If the leak is major and the repair is expensive, you should consider replacing your air conditioner, especially if it’s old.
Learn more about if you should repair or replace your air conditioner.
Need professional help? If your AC still freezes up after you’ve changed the filter and opened all your vents, you’ll need a professional’s help.