Frozen AC Pipes Explained

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Updated February 4, 2023

Even if you have a top-rated air conditioning unit, you may find ice buildup on your AC unit. A frozen AC pipe is a common issue for air conditioning systems, especially during the middle of summer. Without regular maintenance, this can lead to higher energy bills and diminished indoor air quality. So, if you’re wondering, “Why are my air conditioner pipes freezing?” this guide can show you the most common reasons:

  • Poor Airflow Over Evaporator Coils
    • Proper airflow is a critical component in a well-functioning air conditioner. Parts like the blower fan, vents, and air filter work together to ensure consistent airflow over the evaporator coils. If there isn’t enough warm air flowing over the evaporator coil, the refrigerant gets too cold, leading to icy coils.
  • Dirty Evaporator Coil
    • A dirty evaporator coil cannot efficiently absorb the warm air from your home, leading to the refrigerant getting too cold. You can clean your coils with water and soft scrubbing.
  • Dirty Air Filter
    • A dirty air conditioning filter will restrict the AC system’s airflow, leading to an overheating AC system and frozen coils. Luckily, replacing your AC filter is a simple process if you have the correct size air filter.
  • Clogged Air Vent
    • Ensure that your supply and return vents are unobstructed and clean. Closed vents constrict the airflow, leading to insufficient circulation over the evaporator coils.
  • Faulty Blower Fan
    • If your blower motor malfunctions, your AC unit cannot force air over the evaporator coil. If it is the blower motor, you need to contact an AC expert to repair it.
  • Low Refrigerant Levels
    • Your evaporator coil relies on coolants like Freon or Puron to extract heat from your room and expel it through the compressor. Your coolant level might be low if you hear noises from your AC or experience higher-than-usual electric bills. Low refrigerant levels will cause your evaporator coil to become cold and icy.
    • Low refrigerant levels are a definitive sign of a leak, so you need to contact a repair professional to correct the issue.


  • Air conditioning pipes freeze when the refrigerant in the lines gets too cold.
  • If your AC system has an airflow issue like dirty air filters or a faulty blower motor, the warm air from your home cannot adequately warm the refrigerant.
  • Low refrigerant levels in the evaporator lines will cause the pipes to get too cold, leading to frozen evaporator pipes.

Frozen air conditioner pipes can indicate poor airflow or a refrigerant leak. For example, if your air conditioning system stops working at night, it’s probably weak airflow from a dirty filter.

Inspecting your AC filters is a simple task, whether you’re performing routine maintenance on a window AC or central system. In addition, it will keep you clued into any potential issues that call for an air conditioning professional.

Insider Tip

You should contact an HVAC technician if your frozen AC lines are caused by a bad blower motor or leaking refrigerant lines.


It is illegal for non-licensed users to handle refrigerants like Freon or Puron, so you must contact an AC repair professional to replenish your refrigerant levels.

STAT: A 2020 US EIA (Energy Information Agency) survey shows that 17% of Americans use a window AC unit. (source)


What should I do when your AC unit freezes up?

If you have frozen AC coils, you should immediately turn off the air conditioning system. Next, switch the blower fan to “on” and allow the AC unit to defrost. The thawing process should take between one to three hours, and then you can reactivate your air conditioner.

Why is my home’s AC blowing warm air?

Hot air from your AC vents is a common sign of an overheating AC unit. The blower fan is still operational, but there is a failure in the heat exchange process. You could have a dirty air filter restricting airflow, or a severe issue, like a lousy refrigerant line.

Can I pour hot water on a frozen air conditioner?

You can pour water on the frozen air conditioner line if you need your AC quickly back online on a hot summer day. Even lukewarm or room-temperature water will quicken the defrosting process, but you should contact an expert technician if the freezing problem persists.

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