Common Causes of a Frozen Air Conditioner & How To Fix Them

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Although there could be several reasons for a frozen air conditioner, we will talk about the top 8 common causes. So without further adieu, here are the most common reasons your air conditioner may be froze, and how to get it fixed.

Insufficient Airflow

The most common cause of a frozen AC is due to insufficient airflow. Open the indoor air handler compartment to check if the evaporator coils are frozen. If that seems like a massive task for you, you can pull back the black insulation on the copper pipe and you will see some ice forming there. You may also find ice at the outdoor copper piping as well.

Issue: This freezing is the result of insufficient air-flow over your indoor evaporator coils. Clogged air filters are often the cause for this airflow issue. As a result of the air slowing down too much, the refrigerant gets too cold and will cause the coil to freeze. Also, the refrigerant is not heated while in the indoor coil and then returns to the outdoor compressor, which could damage your compressor. You wouldn’t want to do that, because it’s a very expensive part to replace. An HVAC system is designed to work in a way so that the returning refrigerant is warm and it can remove its heat outdoors.

Fix: Turn off your system.  You will then want to wait until all the ice has melted. Open your air filter and clean it properly until it is free of any clogs. Remember, it’s very important to change (or at least check) the air filters every 30 days.

an extremely dirty indoor coil

Dirty Evaporator Coils

If you haven’t been replacing your air filters correctly, or it has been a long time since an HVAC technician visited you, then this definitely might be the cause to your frozen air conditioning unit.

Issue: The evaporator coil must be cleaned to operate smoothly. Debris on the coils could mask the conduction (the transfer of heat from the indoor air), and won’t operate efficiently. The dirt will also restrict the airflow across the coil just as in example 1 above.

Fix: You may have to clean your evaporator coils. This is a bit difficult, and you should only proceed further with the correct knowledge. If you question anything during the process, please stop and give us a call or schedule a call online. We will be more than happy to help you and prevent injuries and even death!

Blocked or Leaked Ducts

The ductwork, that is typically spread across your attic, transfers the cooled air into your rooms. If your HVAC system in your house was designed and installed properly, you should have the proper amount and sized supply and return ducts. However, if you have any blocked vents and registers around your house, you will have an issue with poor airflow. Don’t think that closing off vents would save you some money. In fact, closing registers can result in increased energy consumption. It will only increase your energy bills and not cool your room effectively.

Issue: Not enough air is able to heat the refrigerant flowing through the indoor coil. This will result in a coil that gets too cold and freezer up.

Fix: Look around your home to ensure all supply or return registers are not blocked. Sometimes these vents get unintentionally blocked by furniture or clothes.

Insufficient Refrigerant

Typically, low refrigerant is the least common issue you will run into. Although, the salty air has been known to cause corrosion in the metal components that make up the refrigeration circuit. Leaks can also occur due to two parts of your system rubbing and vibrating against each other.

Issue: Refrigerant can leak from the smallest of holes, and some times these holes are too small for the naked eye. We have also found that some people attempt to use the refrigerant as a source of getting high. This does not work!! So don’t do it!! 

Fix: Be sure to call a professional company to add refrigerant to your system. Adding the incorrect refrigerant can result in thousands of dollars worth of repair bills. We must also weigh in the charge and measure to a precise sub-cooled point. If these measurements are not being taken, then the person charging the system is simply guessing at what they are adding to the system. We also recommend having a leak search performed on your system to locate the possible source of the refrigerant leak.

Malfunctioning Motor

If your airflow is minimized, it could also be due to a failed blower motor. This is a part of your A/C system that blows the air over the indoor evaporator coils.

Issue: When the blower motor does not function along with the rest of the system, the evaporator coils do not get enough air, and eventually it ends up frozen. This is similar to reason # 1 listed above.

Fix: You may want to call your local HVAC company, as it requires advanced equipment to repair it.

Outdoor Temperature

In order for an A/C to work efficiently, the outdoor temperature must be within a certain range. A perfect A/C may show disturbances if the temperature outside is too low. This can result in a frozen evap coil. It is a very common problem in places where the day is warm and the night is very cold.

Issue: When an AC is turned on during cold weather, the pressure inside the unit drops and may cause your AC to freeze up.

Fix: Well, you can’t change the weather outside, so, for the sake of your AC, keep it turned off during the time. You can also call us to have a part called a “head pressure control” relay installed. This will work when it is just slightly cold out, but not in extreme temperatures.

Icebound Nest Thermostat mounted to the wall

Thermostat Issues

Generally, it happens if you have those “old-school” thermostats.

Issue: The “old-school” thermostats are easy to get miscalibrated, as a result, it could function the opposite way your AC control system wants it to. In general, if you do not have a digital thermostat, you need one…

Fix: Buy a new, updated digital thermostat. We carry a full range of thermostats on our vans, and we are also a ProNest dealer. If you order one online, feel free to give us a call if you need assistance installing it. We also carry a ton of extremely smart home automation systems as well!

Clogged Drains

 As we all know, air contains moisture. When your AC blows away the air from your room, the moisture has to go somewhere, right? It is designed to exit through a drain line and then into a pan, and finally into a drain.

Issue: If the drain line gets clogged with debris, the water can’t escape. It might return back into the air handler and damage the air conditioning system, as well as damage your walls and ceiling. If not repaired soon, it can cause mold and mildew growth! That growth on the indoor coils will begin to clog the coil and restricting the airflow. This restricted airflow will result in frozen air conditioning coils. You will also begin breathing that growth!  

Fix: Clear the brush and debris from the exit point of the drain line from the home. If the problem isn’t fixed, call your HVAC technician, immediately!

In Summary

Only try these steps, if you are confident enough and looking for an adventure. Almost all problems of an air conditioner can be easily prevented with regular maintenance by a professional HVAC technician. It is seen that servicing your AC each spring could cost you less money than not servicing it and you could then end up with a bigger issue…costing you way more money.

We recommend you to hire our professional HVAC experts to save you from the hassle when your AC suddenly stops working during a tremendously hot day!