Why is My Window Air Conditioner Freezing Up?

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Updated August 13, 2022

Even a premium air conditioning unit will suffer from common issues without regular maintenance and occasional professional service. For example, if you have a frozen window AC unit, some simple air conditioning repair hacks can quickly address the problem. If you’re having issues with your AC unit, read on to learn, “Why is my window air conditioner freezing up?”

KEY TAKEAWAYS:

  • Ensure that your AC air filters are clean because a dirty filter causes insufficient airflow to the coils.
  • Dirty evaporator coils cannot efficiently absorb heat, leading to coils that get too cold.
  • Refrigerant leaks and broken fan motors disrupt the AC heat exchange and require professional service.

If, instead of your AC spitting out ice, you see water, read our guide on how to fix an AC unit water leak.

Insider Tip

Tilt your window unit about 15 degrees so the condensate drainage can leave the air conditioner efficiently.

Why Air Conditioner Freeze-Ups Happen

If your air conditioner window unit keeps turning off, it could be a wiring issue or frozen evaporator coils. Luckily, you can check for signs of damage and perform window AC unit maintenance to fix most problems. That said, never hesitate to call an air conditioning repair service for electrical or control board wiring issues.

Dirty Air Filter

If you’re unsure what to do when the air conditioner gets too hot or if the coils freeze, replacing the air filter is a great first step. A dirty filter is the most common culprit of a freezing unit. Without a clean filter, your AC will have insufficient airflow to operate efficiently. Additionally, a clogged air filter cannot filter your air, leading to increased allergy symptoms and reduced indoor air quality.

Dirty Evaporator Coil

If your evaporator coils are covered in dirt and grime, your AC cannot efficiently perform the heat exchange needed to cool your home. Once the coils get too dirty, warm air cannot contact them as efficiently, causing them to freeze.

Refrigerant Leak

AC coolant operates in a closed-loop system, so a refrigerant leak isn’t typical, and it requires attention. Without enough refrigerant, your AC cannot efficiently cool the air. Additionally, the coolant needs to expand as the levels drop, leading to lower-than-normal temperatures and frozen coils.

Warning

Homeowners cannot top off their AC’s refrigerant levels because only a licensed air conditioning repair company can legally handle AC coolant.

Broken Fan Motor

The air conditioner fans ensure consistent airflow through the window unit. If the fans are broken, loose, or disconnected, your AC cannot pass warm air over the refrigerant coils. Without that warm air, the refrigerant gets too cold, freezing the window AC coils.

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

Why Is My Window Air Conditioner Freezing Up FAQs

How does a window air conditioner unit work?

The AC thermostat senses the temperature when your indoor temperature rises, activating the blower motor. The indoor air is pulled into the unit and cooled over the evaporator coil. The cooled air is then pushed into your home, lowering the indoor temperature.

How do I remove ice buildup from a frozen air conditioner?

You should turn off a frozen air conditioner. Next, turn the fan on, and allow the ice to thaw over a few hours. If everything checks out, you can restart your AC system.

Can I pour hot water on a frozen evaporator coil?

You can quicken thawing on a frozen AC unit with hot, warm, or room-temperature water. Make sure you disconnect the AC from power before spraying the frozen coils with water.
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