A frozen air conditioner is an issue many people have experienced with their home cooling system. When your air conditioner seems less effective than usual, take a peek “behind the scenes” to see the inner workings. If you notice ice on any of the external components of the AC unit or if the interior is dripping wet, your air conditioner is frozen – and there are a few things you should know.

Here are some of the indicators that your AC unit is freezing up:

  • The copper piping is coated with a thick layer of ice.
  • The filter is soaked.
  • The evaporator coil is a solid block of ice.

So what’s making your air conditioner freeze up? There are a number of possible causes.

Your Filter Is Dirty

A filthy filter is a common cause of a frozen air conditioner. In order to run properly, your AC unit needs adequate airflow, which is impeded when your air filter is dirty. If this is the case, you need to clean or replace it. A dirty filter does serious damage to your AC unit, beyond causing it to ice up:

  • When your filter is blocked, your system works much harder than it needs to. This shortens the lifetime of your air conditioner by burning out the motor, at which point you must replace the whole unit.
  • A dirty filter affects the air quality in your home. The filter is meant to remove allergens (dirt, dust, pollen, dander, mold and mildew) from the air that’s being pumped into your home. HEPA air filters are extraordinarily effective, but even a high-quality HEPA filter is rendered ineffective when it’s clogged.

The filter is an important component of your air conditioner, and if you’re not maintaining it properly, expect problems to continue popping up. If you’re performing regular maintenance on your HVAC systems, your filter should be changed at least once a month. If you’re not performing regular maintenance, you should be. Many of the routine tasks are easy enough to be handled by a homeowner, but others are best left to the professionals. Contact an HVAC service technician to take a look at your system seasonally or biannually and make sure everything is running properly.

It’s Too Cold Outside

This issue becomes more prevalent when the seasons change. As the weather cools down (especially on cool nights in late summer or fall), your air conditioner is more likely to freeze up. Keep in mind that the AC unit needs to cool the air to 18-20 degrees less than you’d like your house temperature to feel. So if it’s cold at night and your thermostat is cranked low, your air conditioner may be frozen by morning.

You’re Low On Freon

It may seem counterintuitive, but low refrigerant levels cause your AC unit to ice up. Without enough refrigerant, the evaporator coil inside your air conditioner gets too cold. As condensation forms, the cold evaporator coil turns this condensation into ice. That’s why one of the biggest manifestations of a frozen AC unit is an evaporator coil that’s turned into a block of solid ice.

Low Freon levels may be easily fixed with a recharge, but they’re often indicative of a problem. If there’s a Freon leak in your system, get in touch with a professional promptly: Reach out to a Comfort Consultant at the On Time Experts. Freon is a dangerous chemical and should only be handled by licensed contractors, so don’t try to fix a Freon leak or replenish low refrigerant levels on your own.

Your Fan Is Faulty

If the fan in your air conditioner is not functioning properly, air doesn’t circulate through the ductwork. As mentioned previously, improper airflow leads to “cold spots” that turn condensation into chunks of ice.

Your AC Unit Doesn’t Know When To Call It Quits

When the contactor in your AC unit is obstructed – most often by insects, dirt and debris – it prevents the system from knowing when to shut off. If the system is running unabated day and night, it quickly seizes up with ice.

Your Vents Are Blocked

Blocked vents restrict the airflow to the evaporator coil, which causes freezing. Just like a dirty filter, any vent obstruction impedes proper air circulation. Without proper circulation, cold air may concentrate in a particular area and cause ice to form.

Your AC Unit Is A Has-Been

HVAC systems have finite lifetimes (despite our hopes that they’ll live forever), and they lose efficiency as they age. If your AC unit is ten years old and has been experiencing frequent freezes, it’s probably time to look for a replacement.

Your family’s comfort is important. So when your AC unit starts to ice up and your home is no longer as cool as it should be, you need to determine what’s wrong and the best solution to fix it. The smartest way to avoid issues like a frozen system is to get routine maintenance and seasonal tune-ups for your HVAC systems.

For help diagnosing and treating problems with your HVAC systems, contact the On Time Experts. A Comfort Consultant is standing by to help keep your family comfortable year-round.

Meet the Author
Randy Kelley
Randy Kelley


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