Why do AC coils freeze?

Author: Chasity Goyette  |  Last update: Sunday, August 3, 2025

Refrigerant leaks are a common cause of frozen coils. Refrigerant is the chemical that runs through your AC coil, changing pressure and temperature in order to absorb heat. If it leaks, the lack of pressure will make it absorb more heat than it should. This makes the refrigerant lines, and then the coils, freeze over.

How do I keep my AC coils from freezing?

Ways To Prevent AC Freezing Up
  1. Replace your air filter frequently. Change the air filter at least once a month to keep your system operating efficiently. ...
  2. Clean the fan. ...
  3. Don't close the vents. ...
  4. Clean the coils on the condenser. ...
  5. Plan a professional inspection.

What causes frozen evaporator coils?

Reasons Why Your AC's Evaporator Coil is Freezing Up

The most common reason for this is that the air conditioner is getting insufficient airflow, which is commonly caused by clogged air filters, backed-up drain clogs, or a low fan speed.

Can you run AC with frozen coils?

Continuing to run your air conditioning unit with frozen evaporator coils poses a significant risk, potentially leading to permanent damage to your entire cooling system. Neglecting to address and unfreeze the AC coils can result in system overheating, which may cause refrigerant leaks and damage to other components.

Will AC freeze if it runs too long?

If the thermostat malfunctions and detects the wrong temperature, this can cause your A/C to run too hard for long periods of time. If your A/C runs for too long it can cause the coils to freeze.

Why Does The Evaporator Coil Freeze (And How to Diagnose It)

How to know if AC is low on refrigerant?

Warning Signs of Low Refrigerant in Your AC or Heat Pump
  1. Weak Airflow or Warm Air Blowing from Vents. ...
  2. Poor Cooling Performance. ...
  3. Constant Cycling On and Off. ...
  4. Ice Buildup on Refrigerant Lines or Evaporator Coil. ...
  5. Hissing or Bubbling Noises.

Is it bad for central AC to run constantly?

Is your central air conditioner is running constantly? This leads to a big energy bill and can even damage your cooling system!

Should I turn my AC off if it's frozen?

1st Step: Turn Your HVAC Unit Off.

Even if it's sweltering outside, you still need to turn OFF your air conditioner! Running a frozen air conditioner will wear out parts much faster, and could overheat your unit. Worn parts are bad news for the most expensive piece of your HVAC unit—the compressor.

Does low Freon cause coil freeze?

Low refrigerant can also lead to frozen evaporator coils. Without refrigerant passing through the coils, there will be no way for that absorbed heat to be transferred out of the air handler. The lack of pressure within the coil continues to drop, the moisture freezes onto the coils, and ice forms as a result.

Do you turn your unit off to make the coil unfreeze?

When you're ready to figure out how to fix a frozen evaporator coil, keep these seven essential tips in mind.
  1. Turn Off the AC Unit. First and foremost, if you suspect a frozen AC coil, turn off your AC system. ...
  2. Let It Sit. ...
  3. Check Filters. ...
  4. Switch On the Fan. ...
  5. Use a Hair Dryer. ...
  6. Let Coils Dry. ...
  7. Clean the Coils.

Can a dirty filter cause AC to freeze?

When the filter becomes dirty, this can block airflow and cause the evaporator coil to get too cold, which can lead to a frozen AC unit. As a general rule of thumb, many HVAC professionals recommend replacing the air filter every 90 days.

How to fix an air conditioner that freezes up?

Turn the Thermostat Fan Setting to On. Turn your thermostat fan setting to “On” so that the fan continues to blow air over the coil. The warm air in the home will naturally defrost the frozen coil. In severe cases, the heat can be turned on to speed up the process.

How to check refrigerant level in AC?

Steps for Checking Refrigerant Levels
  1. Turn Off the AC and Remove the Cover. Turn off the AC unit and remove the cover to access the refrigerant level gauge or gauges.
  2. Locate and Remove the Access Panel. ...
  3. Attach Refrigerant Pressure Gauges. ...
  4. Interpret Pressure Levels. ...
  5. Add Refrigerant (if Necessary)

Can a bad thermostat cause coils to freeze?

An issue with the thermostat can cause your AC to run longer or more frequently. If the AC coils are freezing, the unit may be working more than it needs to. Have the system checked by a professional if your home is too cold or the indoor temperature fluctuates.

How to unclog a condensate drain?

To unclog an AC drain line, turn off the power to the unit. Locate the drain line and use a wet/dry vacuum to suck out the clog. Flush the line with water using a garden hose or cup of water. Check and clean the drain pan under the indoor unit.

What does it mean when your coils freeze up?

The most common reason for frozen evaporator coils is insufficient airflow. This is commonly caused by a clogged or dirty air filter, backed-up drain clogs, low fan speed, or a dirty evaporator coil. Check to see how many registers are closed in your home.

How to stop ice forming in AC?

How to prevent ice formation in your AC
  1. Regular maintenance.
  2. Change the air filters.
  3. Unblock the air vents.
  4. Check the thermostat settings.
  5. Inspect the fan.
  6. Maintain adequate insulation.

Can a dirty condenser cause a coil to freeze?

If mold and grime fill the drain, it also causes water to flow backward into your evaporator compartment. Since the evaporator coil is the coolest during a cycle, nearby water will freeze, almost instantly forming ice crystals.

Can I run my AC with frozen coils?

No, you should not run your AC with frozen coils. Operating the system while the coils are frozen can cause further damage to the unit, leading to costly repairs.

How long to leave AC off to unfreeze?

Well, the thawing process could take up to 24 hours depending on the size of your unit, the extent of the ice buildup, and the efficiency of your blower fan. If the freezing on your air conditioner was just starting, it could clear up faster in an hour or two.

Is it bad for an AC to freeze up?

Air conditioners may be cooling systems but they are not meant to freeze up. It is not part of their design. If it happens, then the cooling system is not working as intended. It will not be able to cool down the house as well as it should.

Do air conditioners need to rest?

Allowing your air conditioner to rest is an excellent way to extend its life and ensure it operates efficiently throughout the years. Air conditioners, like homeowners, require rest in order to recover and perform optimally.

How many years does a central AC last?

While every unit is different, and every homeowner has a different understanding of when their central air conditioner is broken beyond repair, it's fair to say that, with proper maintenance and care, you can expect a good 15 to 20 years of cooling from a new high efficiency air conditioning system.

Should you give your AC a break?

This will reduce the strain placed on your AC unit, allowing it to run more efficiently, and lowering your energy bills. Bottom line, while it's not necessary to give your AC unit rest breaks during summer, its maintenance is essential.

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