Is Your A/C In A Deep Freeze? Here's How To Thaw It Out

On a hot summer's day, ice is something you should see in a tall glass of iced tea and not on the outside of your air conditioner or heat pump. It goes without saying that seeing ice on your A/C is highly unusual and, in most cases, a key indicator of a problem that needs to be taken care of.

Why Does It Form in the First Place?

As your A/C system removes latent heat from the surrounding air, it's also condensing moisture that was once trapped in that warm air. Under normal circumstances, the evaporator coil is kept above freezing temperatures. However, there are many issues that can cause these temperatures to drop, causing the condensed moisture to freeze and form ice over the coil:

  • Poor air flow – The evaporator coil requires a constant flow of air; otherwise, the moisture on the coil will collect and freeze over, causing further blockages.
  • Low refrigerant – Low refrigerant levels are usually caused by leaks or improper servicing. As your A/C system runs low on refrigerant, the resultant drop in pressure causes a corresponding drop in surface temperatures. You can experience the effect for yourself by continuously spraying a can of compressed air until it runs empty.
  • Low outdoor temperatures – A/C systems can freeze up at night, when a combination of low outdoor temperatures and a low thermostat temperature setting can cause sheets of ice to form on the unit.
  • Mechanical issues – A mechanical malfunction, such as the failure of an expansion valve, could cause the coil to freeze over.

Breaking the Ice

The first thing you should do is turn the air conditioner off and let it rest for a few hours. You'll want to turn off power to the unit at the circuit breaker to make sure it doesn't accidentally start up. If you're using your heat pump to cool your home, chances are it has a defrost feature that can get the job done without shutting the heat pump off.

The last thing you'd want to do is attempt to scrape or chisel the ice off. The evaporator coils are very fragile and subjecting them to the forces of a typical de-icing could easily damage these components. The best thing to do is to wait for the ice to melt on its own.

Once your A/C system has completely defrosted, you can take the following steps to track down the problem:

  • Check the airflow – First, make sure there isn't any furniture or any other obstacle blocking the return air vent. Next, check the return air vent itself for any blockages. At this point, you may want to change the air filter, especially if it's caked with dust and debris.
  • Check for leaks – Take a close look at the evaporator coil, compressor and refrigerant lines. Pinhole leaks can cause refrigerant and oil to seep out, causing low refrigerant issues.
  • Check for mold – It's quite possible for mold and mildew growth on the evaporator coil to create blockages and cause freeze-ups. Make sure the evaporator coil is kept clean and free of debris. You might also want to consider an ultraviolet (UV) lamp as a precaution against mold and other biological contaminants.
  • Have a professional check the refrigerant levels – Handling high-pressure refrigerant is something that should be done by a skilled professional with the proper equipment.

Keeping Your A/C Frost-Free

There are plenty of steps you can take to keep your A/C system from turning into a block of ice in the future. For instance, a precursory A/C system check by your HVAC technician can preemptively spot problems that could lead to freeze-ups. Changing your A/C system's air filter on a monthly basis can also help prevent frost issues.

Keeping your A/C system clean and well-maintained are the keys to preventing summertime freeze-ups in the future. You can contact an AC repair service online at