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Why Is My Air Conditioner’s Refrigerant Line Covered in Ice? A Phoenix Tech Explains

Yikes! Your outside air conditioning refrigerant line is covered in ice—which seems crazy in Arizona heat.

So what’s the deal?

Chances are, your indoor unit’s evaporator coil is frozen solid and cold liquid refrigerant is flowing to the outside unit through the refrigerant line (which is why it’s covered in ice).

DO THIS RIGHT NOW: Turn off your AC and turn the fan setting to “ON.”

Heads up: This is NOT a permanent solution. This will simply unfreeze the evaporator coil and prevent any damage to the compressor (a very expensive part you don’t want to replace). Unless you have a professional determine the root problem, your AC will continue to freeze back up every time you turn it on.

To help you protect your AC (and your wallet), we'll explain:

Want to skip the hassle of troubleshooting and have a trained tech repair your AC? We can help!

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What causes the evaporator coil to freeze up

An evaporator coil, a group of copper tubes, freezes when the refrigerant flowing through the tubes gets too cold, causing the moisture in the surrounding air to freeze.

A central AC evaporator coil.

A central AC evaporator coil.

So what causes the refrigerant to get too cold? Usually, it’s one of two things:

  • Low airflow over the evaporator coil
  • Low amounts of refrigerant

What can cause these two problems?

Let’s divide the possible causes into things you can solve right away and things you’ll need a technician to solve.

Try these DIY fixes before calling a pro:

  • Check for a clogged/dirty air filter—A dirty filter reduces airflow over the evaporator coil, causing it to freeze. Check the filter at least once a month and change it if there's a visible layer of dirt.
  • Check for any closed supply vents—OPEN any closed supply vents (the vents that blow air out) immediately—even those in unused rooms. Closing vents reduces airflow over the evaporator coil. Related: Why Closing Air Vents in Unused Rooms Harms Your AC.
  • Check for blocked return vents—Ensure that furniture or curtains aren’t blocking the return vents (the grates where air gets sucked in). Like closing supply vents, this reduces airflow over the evaporator coil.

DIY tips didn't work? You might have one of these issues...

  • Refrigerant leak— The main cause of low refrigerant is a refrigerant leak. The technician needs to evacuate the remaining refrigerant, and then find and—if possible—fix the leak. Related: 4 Signs Your AC May Need More Refrigerant.
  • Malfunctioning indoor blower— If the blower isn’t working properly, there may not be enough air blowing over the evaporator coil, causing it to freeze up. Related: How Much Does It Cost to Replace an AC Blower Motor?
  • Dirty evaporator coil—Dirt blocks airflow over the evaporator coil, causing it to freeze up.

Note: This list isn't exhaustive; it’s just a quick overview of common problems.

Summary: What now?

If you've completed our DIY tips but your AC is still freezing up, you need a technician’s help right away.

An air conditioner that continues to freeze over will eventually let cold refrigerant flood the compressor, which leads to a $1,500+ repair and no cool air.

Contact us today and we'll send a Phoenix tech right over.

If you live in the Phoenix metro area, schedule a repair with George Brazil Air Conditioning and Heating.