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Ice Buildup on your AC Unit

Is your AC running but not blowing out cold air? This is a common problem we see in the summer months and it’s usually due to ice buildup on the AC unit’s refrigerant lines. Some can’t believe the presence of ice is possible because of the hot and humid Iowa weather but believe us, it is.

If you have ice building up on your AC refrigerant lines, you have one of the following 2 problems:

  • Restricted airflow over evaporator coils
  • Low refrigerant levels

Restricted Airflow

When your AC can’t “breathe” in enough air, the part that actually cools the air (the evaporator coil) gets too cold and eventually freezes over. Normally, there’s enough warm unconditioned air passing over those coils to prevent ice or frost build-up. When there’s not enough warm air passing over your evaporator coils, the evaporator will quickly ice over (and ice will travel along the refrigerant lines). The ice builds even faster as humid air hits the coils, condenses and freezes.

Problems that can lead to restricted airflow include:

  • A clogged air filter
  • Collapsed air ducts
  • Dirt on your evaporator coil
  • Blower fan problems
  • Closed or blocked vents

Low Refrigerant Levels

If refrigerant levels drop, the refrigerant pressure inside your evaporator coil drops as well. Then, the pressure drops and so does its temperature. Eventually, the low refrigerant temperatures cause ice to form on evaporator coils. Only one thing causes your AC’s refrigerant levels to drop: a refrigerant leak. Unlike gas in a car, refrigerant never gets “used up”. So if you have low refrigerant levels, the only explanation is that refrigerant has found a way to escape.

What to do if you have ice building up:

  • Move the thermostat setting from COOL to OFF immediately.
  • Turn the thermostat fan setting to “ON” and wait 3 to 4 hours before turning your unit back on. The ON setting runs the fan even when the AC itself isn’t cooling. So, the fan helps draw in warm unconditioned air from your home and blows it over those cold coils to speed up the thawing process.
  • Check your air filter and replace as needed.
  • Check all return vents. Make sure that they’re open and not blocked by furniture/drapes/etc. 
  • Have a Lenz professional come out and assess the problem.

If we are scheduled to come take a look at the unit, our technicians cannot work on the AC if there is still frost present. Be sure to let it completely thaw out before your scheduled time.