Why Does an Air Conditioner Freeze Up?

How does an air conditioner freeze up when it is 95 Degrees outside?

There are several reasons why your air conditioner would freeze up but the main culprit is that you are low on refrigerant, which means you probably have a leak.

A leak will cause not enough pressure for the cold air that is generated by the condenser(the unit that sits outside of the house) to push the cold air into the house and pull the hot air out of the house. Since the coolant isn't circulating, the condenser just continues to get colder and colder because the thermostat isn't getting cooler and tells that air conditioner to continue to run. Soon your condenser will look like a block of ice and will freeze up.

Here are a couple of signs that you are leaking coolant:

  • It takes a long time to cool your home
    • Refrigerant is what absorbs the heat from inside your home and carries it outside. If there isn't enough coolant or pressure to move the heat out and bring the cool air in, the air coming out of your register will be warm
  • "Oil "Dripping from your coolant lines around your furnace.
    • Mixed with the coolant is a little bit of lubricant mixed with the coolant to keep things running smoothly. When there is leak, the coolant escapes(might be in gas form at this point) but the oil is pushed out as well. This leak in the picture above is from years of leaking.

So what can you do about it?

  • Have a trained professional look at it to diagnose the problem
    • You are probably going to have a couple options
      • Charge the system with new refrigerant AFTER you find the leak and have that repaired(this should be a one time fix because coolant doesn't disappear)
      • Based on the age and coolant type, replacement options might be the way to go
      • Replacing or Repair?  
      • R-22 Refrigerant Phase-Out
  • Get on a maintenance plan that will help find those problems before they become ice cubes


Since your furnace and air conditioner work together, it is important that they work in tandem correctly and efficiently. A condenser that freezes up will not only cause problems with your air conditioner but over time could cause problems with your entire HVAC system.