AC Line Frozen: 5 Causes to Freeze and How to Fix It

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An air conditioning system provides cool air to the room, sometimes at freezing temperatures. However, the unit often stays warm internally, which is why a frozen AC line indicates a problem with your unit.

In this article, we take a look at the 5 most common causes for a frozen AC line, and how you can troubleshoot them. We'll also provide helpful tips to prevent an AC line from freezing, and to keep your air conditioning unit in good working condition for longer.

Cause Description Solution
Blocked Vents Obstructions around supply vents are causing air flow to stay within the AC unit, freezing up the coils. Remove the obstructions surrounding the vents.
Dirty Filter and Coils Dust accumulation insulates the coils, and locks in moisture that freezes up. Clean the air filters and evaporator coils once every two weeks.
Refrigerant Leak Refrigerant causes moisture in the unit to freeze up. Have a professional technician find and fix the leak.
Cold Temperatures Cold outdoor temperatures are freezing the moisture inside the air conditioner. Let the AC unit thaw out, and avoid using the unit during cold weather.
Blower Fan Failure Malfunctioning blower motor cannot properly direct the cooled air out of the unit. Replace the faulty parts.

5 Reasons Why Your AC Line is Freezing Up and How to Troubleshoot Them

There are multiple reasons why your AC line is frozen. Anything from dirty filters to refrigerant leaks can cause a frozen AC line. Not all reasons can be easily fixed at home, and you may need an air conditioning repair service to tackle chemical coolant leaks, and the malfunctioning of internal parts.

#1 Blocked Vents

First, check the supply vents. Are there obstructions blocking the supply vents, causing the cooled air to circulate inside the unit, or are there obstructions making it difficult for the cold air to travel through the room? Obstructions, such as furniture, fixtures, and walls, blocking the air flow from the vents are some of the common reasons why your AC line is frozen.

To troubleshoot, power your AC system off. Check all the vents in both the indoor and outdoor units to see if there are fixtures or debris blocking the supply vents, and remove these obstructions. Let the frozen AC line thaw out before powering the AC system back on, then see if this solves the problem with your air conditioner line.

#2 Dirty Air Filter and Coils

You may notice your AC unit blowing warm air instead of cool air due to a dirty air filter. Besides blocked vents, dust accumulated in filters and coils can also cause a frozen AC line as the debris locks in moisture inside your air conditioning system. As the air conditioner cools the air, it freezes the accumulated moisture surrounding the filter and evaporator coils.

Troubleshooting this problem is fairly simple. Power your AC unit off, then let the frozen AC line thaw. You may use a hair dryer to apply warm air to thaw the ice buildup faster, but this is not necessary. Remove the air filter carefully, and wash it with a combination of soap and water. Vacuum up the dust surrounding the evaporator coils.

#3 Refrigerant Leak

A refrigerant leak is another cause for a frozen air conditioner, however, this issue cannot be easily solved at home. Refrigerant is what cools the air that goes through the air conditioning unit, and when the chemical coolant leaks out, it can freeze up the water accumulation around the evaporator coils.

Refrigerant leaks cannot be solved at home without proper tools. The coolant can be irritating to the skin and lungs, so it is best to have a professional find and fix the leak. A professional HVAC technician will use a colored dye to locate the leak, fix it, and top up your refrigerant to keep your air conditioner in good condition.

#4 Cold Air

If the weather is cold outside, it can cause your air conditioner to freeze. An air conditioner freezes when there is enough humidity inside the unit, coupled by freezing-low temperatures outside. When this happens, your AC unit may blow warm air instead of cooled air, and you may notice ice accumulation around the evaporator coil.

To troubleshoot this, shut down your air conditioner, and check the frozen AC lines. Air conditioners often dehumidify spaces, so check whether a dirty evaporator coil is causing moisture to accumulate inside. Let the frozen AC lines thaw out, and clean the filters and dirty evaporator coil as needed. Avoid using your unit in cold weather.

#5 Blower Fan Failure

You may notice the air flow around your unit getting weaker despite using the highest fan mode setting. This may be due to a problem with your blower fan. A malfunctioning blower fan cannot direct the cooled air out of the unit, while the exhaust unit continues to remove warm air from inside the air conditioner. As a result, the unit’s evaporator coil freezes.

For blower motor and fan blade problems, it is best to leave the issue to the professionals as they will be able to assess and determine the root cause of the problem. Have your faulty fan motor replaced, and have a professional check your air conditioner from the compressor to the evaporator coil for a thorough checkup.

5 Tips to Prevent Your AC Lines from Freezing

Air conditioning systems can be low maintenance units with proper care, as the majority of AC problems are caused by dust and dirt accumulation in the unit. Here are 5 tips you can do to prevent your AC lines from freezing up in the future:

  1. Clean your air conditioner thoroughly. Wash the air filter at least once every two weeks to remove dust accumulation, and vacuum up the evaporator coils as well. Give your outdoor unit a good rinse with the garden hose on a hot day to dislodge any debris inside.
  2. Avoid using your AC unit in cold weather. Cool temperatures can cause moisture inside your AC unit to freeze, so it is best to use the heater setting of your unit, or keep the temperature on a moderately high level to prevent a frozen AC line.
  3. Have your unit professionally checked. Your HVAC system will benefit from a professional checkup by one of our Luce Aircon technicians. Have our technicians check your unit every 4-6 months for the best care.
  4. Avoid overworking your AC unit. An overworked air conditioning system is more likely to break down faster. Use your HVAC systems only as needed, and let the air conditioning unit cool down after a long period of use.
  5. Keep the vents clear. This will keep the air flow circulated around the room, and prevent the cooled air from freezing up your AC line.

When to Call the Professionals

When it's time to call the professionals, contact us at Luce Aircon. Our technicians will be able to clean, assess, and repair any air conditioner problems across most brands and models in Singapore! You can be assured we'll find the cause of the problem, and fix it for good.

Check out our article on aircon ice build up!

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